Statistical Diagrams: Histograms and Cumulative Frequency: Edexcel 4MA1 Past Paper Questions and Worked Solutions
This page collects every statistical diagrams: histograms and cumulative frequency question from the Pearson Edexcel International GCSE Mathematics A (4MA1) Higher tier Paper 1H and Paper 1HR, January 2020 to June 2025: 22 questions worth 99 marks. Questions run from easier to harder. Try each one first, then click “Show solution” for a step-by-step method with the reason for every step. All answers are checked against the official Pearson mark schemes.
The frequency table gives information about the ages of the 80 people in a train carriage.
| Age (a years) | Frequency |
|---|---|
| 0 < a ≤ 20 | 9 |
| 20 < a ≤ 30 | 19 |
| 30 < a ≤ 40 | 17 |
| 40 < a ≤ 50 | 18 |
| 50 < a ≤ 60 | 13 |
| 60 < a ≤ 70 | 4 |
(a) Complete the cumulative frequency table. (1)
(b) Draw a cumulative frequency graph for your table. (2)
(c) Use your graph to find an estimate for the median age of the people in the train carriage. (2)
Show solution
Part (a)
- Running totals: 9, 28, 45, 63, 76, 80
Answer: 9, 28, 45, 63, 76, 80
Part (b)
- Plot (20, 9), (30, 28), (40, 45), (50, 63), (60, 76), (70, 80), starting at (0, 0), and join with a curve.
Answer: Curve through (0, 0), (20, 9), (30, 28), (40, 45), (50, 63), (60, 76), (70, 80)
Part (c)
- The median is the 80 ÷ 2 = 40th person. Read across from 40 to the curve, then down.
Answer: about 37 years (35 to 38 accepted)
The cumulative frequency graph gives information about the weights, in grams, of 90 bags of sweets.
Diagram: Cumulative frequency graph of the weights of 90 bags of sweets, weight 120 to 180 grams on the horizontal axis and cumulative frequency 0 to 90 on the vertical axis
(a) Find an estimate for the median of the weights of these bags of sweets. (2)
Roberto sells the bags of sweets to raise money for charity. Bags with a weight greater than d grams are labelled large bags and sold for 3.75 euros each bag. The total amount of money he receives by selling all the large bags is 93.75 euros.
(b) Find the value of d. (3)
Show solution
Part (a)
- The median is the 90 ÷ 2 = 45th bag. Read across from 45 to the curve and down.
Answer: about 146 grams (145 to 147 accepted)
Part (b)
- Number of large bags = 93.75 ÷ 3.75 = 25
- The 25 heaviest bags are large, so 90 − 25 = 65 bags weigh d grams or less.
- Read across from 65 on the cumulative frequency axis to the curve, then down.
Answer: d = about 151 (150 to 152 accepted)
The manager of a call centre asked the 120 people who rang the call centre last week how long they each waited before their call was answered.
| Time waited (t minutes) | Frequency |
|---|---|
| 0 < t ≤ 5 | 8 |
| 5 < t ≤ 10 | 15 |
| 10 < t ≤ 15 | 17 |
| 15 < t ≤ 20 | 28 |
| 20 < t ≤ 25 | 33 |
| 25 < t ≤ 30 | 19 |
(a) Complete the cumulative frequency table. (1)
(b) Draw a cumulative frequency graph for your table. (2)
(c) Use your graph to find an estimate for the median of the times waited. (1)
(d) Using your graph, find an estimate for the percentage of the 120 people who said that they waited longer than 23 minutes before their call was answered. Show your working clearly. (2)
Show solution
Part (a)
- Running totals of the frequencies.
Answer: 8, 23, 40, 68, 101, 120
Part (b)
- Plot (5, 8), (10, 23), (15, 40), (20, 68), (25, 101), (30, 120), start at (0, 0), and join with a curve.
Answer: Curve through (0, 0), (5, 8), (10, 23), (15, 40), (20, 68), (25, 101), (30, 120)
Part (c)
- Median = the 120 ÷ 2 = 60th person. Read across from 60, then down.
Answer: about 18.5 minutes (17 to 20 accepted)
Part (d)
- Read up from 23 minutes: about 88 people waited 23 minutes or less.
- Longer than 23 minutes: 120 − 88 = 32 people
- Percentage = 32120 × 100 = 26.7%
Answer: about 27% (25% to 29% accepted)
The table gives information about the times taken by 90 runners to complete a 10 km race.
| Time (t minutes) | Frequency |
|---|---|
| 25 < t ≤ 35 | 12 |
| 35 < t ≤ 45 | 24 |
| 45 < t ≤ 55 | 28 |
| 55 < t ≤ 65 | 12 |
| 65 < t ≤ 75 | 10 |
| 75 < t ≤ 85 | 4 |
(a) Complete the cumulative frequency table. (1)
(b) Draw a cumulative frequency graph for your table. (2)
Any runner who completed the race in a time T minutes such that 42 < T ≤ 52 minutes was awarded a silver medal.
(c) Use your graph to find an estimate for the number of runners who were awarded a silver medal. (2)
Show solution
Part (a)
- Running totals: 12, 12 + 24 = 36, 36 + 28 = 64, 64 + 12 = 76, 76 + 10 = 86, 86 + 4 = 90
Answer: 12, 36, 64, 76, 86, 90
Part (b)
- Plot at the upper class boundaries: (35, 12), (45, 36), (55, 64), (65, 76), (75, 86), (85, 90), starting at (25, 0).
Answer: Curve through (25, 0), (35, 12), (45, 36), (55, 64), (65, 76), (75, 86), (85, 90)
Part (c)
- Read the cumulative frequency at 52 minutes (about 56) and at 42 minutes (about 29).
- Silver medals ≈ 56 − 29
Answer: about 27 runners (25 to 29 accepted)
The table shows information about the times, in minutes, that 80 patients had to wait to see a doctor.
| Time (W minutes) | Frequency |
|---|---|
| 0 < W ≤ 10 | 7 |
| 10 < W ≤ 20 | 10 |
| 20 < W ≤ 30 | 15 |
| 30 < W ≤ 40 | 32 |
| 40 < W ≤ 50 | 16 |
(a) Complete the cumulative frequency table. (1)
(b) On the grid, draw a cumulative frequency graph for your table. (2)
(c) Use your graph to find an estimate for the median. (1)
(d) Use your graph to find an estimate for the interquartile range. (2)
Show solution
Part (a)
- Running totals of the frequencies: 7, 7 + 10 = 17, 17 + 15 = 32, 32 + 32 = 64, 64 + 16 = 80
Answer: 7, 17, 32, 64, 80
Part (b)
- Plot each cumulative frequency at the end of its class: (10, 7), (20, 17), (30, 32), (40, 64), (50, 80). Start at (0, 0) and join with a smooth curve.
Answer: Curve through (0, 0), (10, 7), (20, 17), (30, 32), (40, 64), (50, 80)
Part (c)
- Median = the 80 ÷ 2 = 40th patient. Read across from 40, then down to the time axis.
Answer: about 33 minutes (32 to 34 accepted)
Part (d)
- Lower quartile: read across from 80 ÷ 4 = 20, giving about 22 minutes.
- Upper quartile: read across from 3 × 80 ÷ 4 = 60, giving about 38 minutes.
- IQR = 38 − 22
Answer: about 16 minutes (15 to 17 accepted)
A total of 80 men and women took part in a race. The cumulative frequency graph gives information about the times, in minutes, they took for the race.
Diagram: Cumulative frequency graph for the race times of 80 people, time from 20 to 70 minutes on the horizontal axis and cumulative frequency 0 to 80 on the vertical axis
(a) Use the graph to find an estimate for the interquartile range. (2)
60% of the men took 50 minutes or less for the race. No women took 50 minutes or less for the race.
(b) Work out an estimate for the number of men who took part in the race. (3)
Show solution
Part (a)
- Lower quartile: the 80 ÷ 4 = 20th person. Read across from 20 to the curve and down: about 38 minutes.
- Upper quartile: the 60th person: about 56 minutes.
- IQR = 56 − 38
Answer: about 18 minutes (17 to 19 accepted)
Part (b)
- Read the cumulative frequency at 50 minutes: about 42 people took 50 minutes or less.
- No women took 50 minutes or less, so these 42 people are all men, and they are 60% of the men.
- Number of men = 42 ÷ 0.6
Answer: 70
The cumulative frequency graph gives information about the waiting times, in minutes, of people with appointments at Hospital A.
Diagram: Cumulative frequency graph of waiting times at Hospital A for 60 people, waiting time 0 to 50 minutes on the horizontal axis
(a) Use the graph to find an estimate of the median waiting time at Hospital A. (1)
(b) Use the graph to find an estimate of the interquartile range of the waiting times at Hospital A. (2)
At a different hospital, Hospital B, the median waiting time is 28 minutes and the interquartile range of the waiting times is 19 minutes.
(c) Compare the waiting times at Hospital A with the waiting times at Hospital B. (2)
Show solution
Part (a)
- There are 60 people, so the median is the 30th value. Read across from 30 to the curve and down.
Answer: about 23 minutes (22 to 24 accepted)
Part (b)
- Lower quartile (15th value) ≈ 16 minutes. Upper quartile (45th value) ≈ 28 minutes.
- IQR ≈ 28 − 16
Answer: about 12 minutes (10 to 14 accepted)
Part (c)
- Compare an average: Hospital A’s median (23) is lower than Hospital B’s (28).
- Compare the spread: Hospital A’s IQR (12) is smaller than Hospital B’s (19).
Answer: On average waiting times are shorter at Hospital A (lower median), and they are more consistent at Hospital A (smaller IQR)
The table gives information about the times, in minutes, taken by 80 customers to do their shopping in a supermarket.
| Time taken (t minutes) | Frequency |
|---|---|
| 0 < t ≤ 10 | 7 |
| 10 < t ≤ 20 | 26 |
| 20 < t ≤ 30 | 24 |
| 30 < t ≤ 40 | 14 |
| 40 < t ≤ 50 | 7 |
| 50 < t ≤ 60 | 2 |
(a) Complete the cumulative frequency table. (1)
(b) Draw a cumulative frequency graph for your table. (2)
(c) Use your graph to find an estimate for the median time taken. (1)
One of the 80 customers is chosen at random.
(d) Use your graph to find an estimate for the probability that the time taken by this customer was more than 42 minutes. (2)
Show solution
Part (a)
- Running totals.
Answer: 7, 33, 57, 71, 78, 80
Part (b)
- Plot (10, 7), (20, 33), (30, 57), (40, 71), (50, 78), (60, 80), start at (0, 0), and join with a curve.
Answer: Curve through (0, 0), (10, 7), (20, 33), (30, 57), (40, 71), (50, 78), (60, 80)
Part (c)
- Median = the 40th customer. Read across from 40 and down.
Answer: about 23 minutes (21 to 24 accepted)
Part (d)
- Read up from 42 minutes: about 72 customers took 42 minutes or less.
- More than 42 minutes: 80 − 72 = 8 customers
Answer: about 880 (= 0.1)
The cumulative frequency graph shows information about the heights, in centimetres, of 50 plants in a flowerbed.
Diagram: Cumulative frequency curve for the heights of 50 plants, height 0 to 60 cm on the horizontal axis and cumulative frequency 0 to 50 on the vertical axis
(a) Use the graph to find an estimate for the median height of these plants. (1)
(b) Use the graph to find the frequency for the class interval 30 < Height ≤ 40. (1)
(c) Use the graph to find an estimate for the number of plants with a height greater than 35 centimetres. (2)
Show solution
Part (a)
- There are 50 plants, so the median is the 25th value. Go across from 25 on the cumulative frequency axis to the curve, then down.
Answer: about 28 cm
Part (b)
- Read the cumulative frequency at 40 cm (about 44) and at 30 cm (about 30). The frequency for the class is the difference.
- 44 − 30
Answer: 14
Part (c)
- Go up from 35 cm to the curve and across: about 38 plants are 35 cm or shorter.
- Plants taller than 35 cm = 50 − 38
Answer: about 12
The table gives information about the ages of 80 people in a cinema.
| Age (n years) | Frequency |
|---|---|
| 10 < n ≤ 20 | 12 |
| 20 < n ≤ 30 | 15 |
| 30 < n ≤ 40 | 20 |
| 40 < n ≤ 50 | 18 |
| 50 < n ≤ 60 | 9 |
| 60 < n ≤ 70 | 6 |
(a) Complete the cumulative frequency table (classes 10 < n ≤ 20, 10 < n ≤ 30, …, 10 < n ≤ 70). (1)
(b) Draw a cumulative frequency graph for your table. (2)
(c) Use your graph to find an estimate for the percentage of the 80 people who are more than 46 years of age. Give your answer correct to the nearest whole number. (3)
Show solution
Part (a)
- Cumulative frequency is a running total: add each frequency to the total so far.
| Age (n years) | Cumulative frequency |
|---|---|
| 10 < n ≤ 20 | 12 |
| 10 < n ≤ 30 | 12 + 15 = 27 |
| 10 < n ≤ 40 | 27 + 20 = 47 |
| 10 < n ≤ 50 | 47 + 18 = 65 |
| 10 < n ≤ 60 | 65 + 9 = 74 |
| 10 < n ≤ 70 | 74 + 6 = 80 |
Answer: 12, 27, 47, 65, 74, 80
Part (b)
- Plot each cumulative frequency at the upper end of its class: (20, 12), (30, 27), (40, 47), (50, 65), (60, 74), (70, 80). Start at (10, 0) and join the points with a smooth curve.
Answer: Curve through (10, 0), (20, 12), (30, 27), (40, 47), (50, 65), (60, 74), (70, 80)
Part (c)
- Go up from 46 on the age axis to the curve, then across: the cumulative frequency is about 58. So about 58 people are 46 or younger.
- People older than 46 ≈ 80 − 58 = 22
- Percentage = 2280 × 100 = 27.5%, which is about 28%
Answer: 28% (the mark scheme accepts 26% to 29%, depending on your curve)
The table gives information about the times taken by 80 people to run a race.
| Time taken (t minutes) | Frequency |
|---|---|
| 50 < t ≤ 60 | 15 |
| 60 < t ≤ 70 | 16 |
| 70 < t ≤ 80 | 21 |
| 80 < t ≤ 90 | 14 |
| 90 < t ≤ 100 | 8 |
| 100 < t ≤ 110 | 6 |
(a) Complete the cumulative frequency table (50 < t ≤ 60, 50 < t ≤ 70, …, 50 < t ≤ 110). (1)
(b) Draw a cumulative frequency graph for your table. (2)
(c) Use your graph to find an estimate for the median time taken. (1)
(d) Use your graph to find an estimate for the interquartile range of the times taken. (2)
Show solution
Part (a)
- Keep a running total of the frequencies.
Answer: 15, 31, 52, 66, 74, 80
Part (b)
- Plot each running total at the upper end of its class: (60, 15), (70, 31), (80, 52), (90, 66), (100, 74), (110, 80), and start at (50, 0). Join with a smooth curve.
Answer: Curve through (50, 0), (60, 15), (70, 31), (80, 52), (90, 66), (100, 74), (110, 80)
Part (c)
- The median is the 80 ÷ 2 = 40th value. Go across from 40 to the curve, then down.
Answer: about 74 minutes (73 to 75 accepted)
Part (d)
- Lower quartile: the 80 ÷ 4 = 20th value, about 63 minutes.
- Upper quartile: the 3 × 80 ÷ 4 = 60th value, about 86 minutes.
- IQR = 86 − 63
Answer: about 23 minutes (21 to 24 accepted)
The table gives information about the heights, in metres, of the trees in a park.
| Height (h metres) | Frequency |
|---|---|
| 0 < h ≤ 2 | 5 |
| 2 < h ≤ 5 | 12 |
| 5 < h ≤ 10 | 18 |
| 10 < h ≤ 20 | 14 |
| 20 < h ≤ 35 | 9 |
On the grid, draw a histogram for this information.
Show solution
- In a histogram the bar heights are frequency densities: frequency density = frequency ÷ class width.
| Class | Width | Frequency | Frequency density |
|---|---|---|---|
| 0 < h ≤ 2 | 2 | 5 | 5 ÷ 2 = 2.5 |
| 2 < h ≤ 5 | 3 | 12 | 12 ÷ 3 = 4 |
| 5 < h ≤ 10 | 5 | 18 | 18 ÷ 5 = 3.6 |
| 10 < h ≤ 20 | 10 | 14 | 14 ÷ 10 = 1.4 |
| 20 < h ≤ 35 | 15 | 9 | 9 ÷ 15 = 0.6 |
- Draw each bar with no gaps, from the start to the end of its class, up to its frequency density.
Answer: Bars at heights 2.5, 4, 3.6, 1.4 and 0.6
The histogram shows information about the times, in minutes, that some people were in a shop. Work out an estimate for the proportion of these people who were in the shop for more than 40 minutes.
Show solution
- Frequency = frequency density × class width. Find the frequency of every bar.
| Class | Width | Frequency density | Frequency |
|---|---|---|---|
| 0–10 | 10 | 2.5 | 25 |
| 10–15 | 5 | 4 | 20 |
| 15–30 | 15 | 3.6 | 54 |
| 30–50 | 20 | 0.5 | 10 |
| 50–60 | 10 | 1.7 | 17 |
- Total number of people = 25 + 20 + 54 + 10 + 17 = 126
- More than 40 minutes: half of the 30–50 bar (40 to 50 is 10 of its 20 minutes) gives 0.5 × 10 = 5 people, plus all 17 in the 50–60 bar. That is 5 + 17 = 22 people.
- Proportion = 22126 = 1163
Answer: 1163 (about 0.175)
The table gives information about the heights, in centimetres, of some plants.
| Height (h cm) | Frequency |
|---|---|
| 10 < h ≤ 20 | 35 |
| 20 < h ≤ 35 | 45 |
| 35 < h ≤ 50 | 75 |
| 50 < h ≤ 70 | 40 |
| 70 < h ≤ 80 | 8 |
(a) On the grid, draw a histogram for this information. (3)
(b) Work out an estimate for the number of these plants with a height greater than 40 cm. (2)
Show solution
Part (a)
- Frequency density = frequency ÷ class width: 35 ÷ 10 = 3.5, 45 ÷ 15 = 3, 75 ÷ 15 = 5, 40 ÷ 20 = 2, 8 ÷ 10 = 0.8
Answer: Bars at frequency densities 3.5, 3, 5, 2 and 0.8
Part (b)
- From 40 to 50 is 1015 of the 35–50 class: 1015 × 75 = 50 plants
- Add the classes above 50: 40 + 8 = 48
- 50 + 48
Answer: 98
The table and histogram give information about the distance travelled, in order to get to work, by each person working in a large store.
| Distance (d km) | Frequency |
|---|---|
| 0 ≤ d < 10 | 40 |
| 10 ≤ d < 15 | |
| 15 ≤ d < 20 | |
| 20 ≤ d < 30 | |
| 30 ≤ d < 60 | 30 |
(a) Complete the table. (2)
(b) Complete the histogram. (1)
One of the people working in the store is chosen at random.
(c) Work out an estimate for the probability that the distance travelled by this person, in order to get to work, was greater than 25 km. (2)
Show solution
Part (a)
- Use the 0–10 bar to find the scale: frequency density = 40 ÷ 10 = 4. That bar is 20 small squares tall, so each small square = 0.2.
- 10–15 is 35 small squares tall: fd = 7, frequency = 7 × 5 = 35
- 15–20 is 39 small squares tall: fd = 7.8, frequency = 7.8 × 5 = 39
- 20–30 is 28 small squares tall: fd = 5.6, frequency = 5.6 × 10 = 56
Answer: 35, 39, 56
Part (b)
- 30–60: frequency density = 30 ÷ 30 = 1, so draw a bar 5 small squares tall from 30 to 60.
Answer: Bar from 30 to 60 at frequency density 1
Part (c)
- Total number of people = 40 + 35 + 39 + 56 + 30 = 200
- More than 25 km: half of the 20–30 class (25 to 30) is 0.5 × 56 = 28, plus all 30 in 30–60, giving 58 people
- Probability = 58200
Answer: 29100 = 0.29
The incomplete table and incomplete histogram give information about the times, in minutes, that 140 people waited at a station for a train.
| Time (t minutes) | Frequency |
|---|---|
| 0 < t ≤ 5 | 23 |
| 5 < t ≤ 15 | |
| 15 < t ≤ 30 | |
| 30 < t ≤ 40 | 18 |
| 40 < t ≤ 60 | 14 |
Complete the table and the histogram.
Show solution
- The two missing frequencies add to 140 − 23 − 18 − 14 = 85.
- The bars have no scale, so compare them. Frequency = width × height, so compare both.
- The 15–30 bar is 1.5 times as wide as the 5–15 bar and 1.6 times as tall (20 small squares against 12.5).
- So if the 5–15 bar has frequency f, the 15–30 bar has 1.5 × 1.6 × f = 2.4f.
- f + 2.4f = 85, so 3.4f = 85 and f = 25. The 15–30 class has 85 − 25 = 60.
- Frequency densities: 5–15 is 25 ÷ 10 = 2.5 and 15–30 is 60 ÷ 15 = 4. So each big square up is 1 and each small square is 0.2.
- Now the missing bars: 0–5 has 23 ÷ 5 = 4.6, 30–40 has 18 ÷ 10 = 1.8 and 40–60 has 14 ÷ 20 = 0.7.
Answer: Table: 25 and 60. New bars: 0–5 at 4.6, 30–40 at 1.8, 40–60 at 0.7
The histogram gives information about the heights of all the Year 11 students at a school. There are 160 students in Year 11 with a height between 155 cm and 170 cm. Work out the total number of students in Year 11 at the school.
Show solution
- No scale is given, so measure each bar’s height in small squares: 18, 40, 20, 15 and 6.
- Use width (cm) × height (squares) as “area units”, because frequency is proportional to area.
- 155 to 170 cm: 5 × 40 + 10 × 20 = 200 + 200 = 400 area units = 160 students, so 1 student = 400 ÷ 160 = 2.5 area units.
- Total area: 15 × 18 + 5 × 40 + 10 × 20 + 15 × 15 + 5 × 6 = 270 + 200 + 200 + 225 + 30 = 925 area units
- Total students = 925 ÷ 2.5
Answer: 370
The histogram gives information about the height, h cm, of each tree in part of a forest. There are no trees for which h ≤ 200 and for which h > 800. The number of trees for which 300 < h ≤ 400 is 8 fewer than the number of trees for which 400 < h ≤ 500. Work out an estimate for the number of trees in this part of the forest that have a height greater than 500 cm.
Show solution
- There is no scale, so measure each bar’s height in small squares: 200–250 is 10, 250–300 is 8, 300–400 is 6, 400–450 is 15, 450–600 is 5 and 600–800 is 1.
- Frequency is proportional to area, so use width (cm) × height (squares) as “area units”.
- 400 < h ≤ 500 = all of the 400–450 bar and the first 50 cm of the 450–600 bar: 50 × 15 + 50 × 5 = 1000 area units
- 300 < h ≤ 400: 100 × 6 = 600 area units
- The difference, 1000 − 600 = 400 area units, represents 8 trees, so 50 area units = 1 tree.
- Greater than 500 cm: the last 100 cm of the 450–600 bar plus the whole 600–800 bar: 100 × 5 + 200 × 1 = 700 area units
- 700 ÷ 50
Answer: 14
The histogram gives information about the weights, in kg, of all the watermelons in a field. There are 16 watermelons with a weight between 8 kg and 8.5 kg. Work out the total number of watermelons in the field.
Show solution
- Use the 8–8.5 bar for the scale: frequency density = 16 ÷ 0.5 = 32. That bar is 32 small squares tall, so each small square = 1 watermelon per kg.
- Read the other bars: 7–8 is 15, 8.5–9.5 is 23, 9.5–10.5 is 30, 10.5–12 is 12.
- Frequencies = density × width: 15 × 1 = 15, 23 × 1 = 23, 30 × 1 = 30, 12 × 1.5 = 18
- Total = 15 + 16 + 23 + 30 + 18
Answer: 102
The histogram shows information about the total time, m minutes, taken by each child in a school to walk to school every day for one week. There are no children for whom m > 100. There are 10 children for whom m ≤ 20. Work out an estimate for the number of children for whom 50 < m ≤ 80.
Show solution
- Use the bar we know to find the scale. 10 children in 0–20 (width 20) gives frequency density 10 ÷ 20 = 0.5. That bar is 2.5 small squares tall, so each small square up = 0.2.
- Read the bars we need: 40–60 has frequency density 2.9, 60–75 has 3.2 and 75–100 has 2.0.
- 50 < m ≤ 80 covers half of the 40–60 bar (50 to 60), all of the 60–75 bar, and 75 to 80 of the last bar.
- 50–60: 2.9 × 10 = 29; 60–75: 3.2 × 15 = 48; 75–80: 2.0 × 5 = 10
- Total = 29 + 48 + 10
Answer: 87
Some people attend a concert. The histogram shows information about the ages of these people. Work out an estimate for the percentage of these people who are aged more than 55 years. Give your answer correct to one decimal place.
Show solution
- There is no scale, but we only need a percentage, so we can measure each bar in small squares. Area is proportional to frequency.
- Using width (in years) × height (in small squares): 20–25: 5 × 16 = 80, 25–30: 5 × 50 = 250, 30–40: 10 × 33 = 330, 40–50: 10 × 19 = 190, 50–75: 25 × 9 = 225
- Total = 80 + 250 + 330 + 190 + 225 = 1075
- Aged more than 55: the part of the last bar from 55 to 75, which is 20 × 9 = 180
- Percentage = 1801075 × 100 = 16.744…
Answer: 16.7%
The incomplete histogram shows information about the distances, in kilometres, that 100 adults ran last week. All of the adults ran at least 5 kilometres. None of the adults ran more than 55 kilometres. 14 adults ran between 15 kilometres and 20 kilometres. Complete the histogram.
Show solution
- The vertical axis has no scale, so use the bar we know. The 15–20 bar has frequency 14 and width 5, so its frequency density = 14 ÷ 5 = 2.8. Its height is 28 small squares, so each small square up is 0.1.
- Read the other bars: 20–35 has height 3.4 and 35–55 has height 0.4.
- Frequency = frequency density × class width: 20–35 gives 3.4 × 15 = 51 adults; 35–55 gives 0.4 × 20 = 8 adults.
- Adults shown so far = 14 + 51 + 8 = 73, so the missing class 5–15 has 100 − 73 = 27 adults.
- Frequency density for 5–15 = 27 ÷ 10 = 2.7, so draw a bar from 5 to 15 with height 2.7.
Answer: Bar from 5 km to 15 km at frequency density 2.7
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