Robinson Tuition
Grade 7 · Higher · free GCSE maths worksheet

Histograms with unequal class widths

Frequency density.

15 original questions, 59 marks. Print the worksheet, mark it with the answers sheet, and use the solutions to see every step written out by hand.

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The questions

1

The table shows the frequency densities for the lengths, l cm, of the worms found in a soil survey.

Length (l cm)Frequency density
0 < l ≤ 51.2
5 < l ≤ 152.1
15 < l ≤ 203.0
20 < l ≤ 400.4

Work out the total number of worms found in the survey.

3 marks
Show answer
50
2

The table shows the times, t minutes, that 53 customers spent in a coffee shop.

Time (t minutes)FrequencyFrequency density
0 < t ≤ 1018
10 < t ≤ 1512
15 < t ≤ 2515
25 < t ≤ 458

Complete the frequency density column.

3 marks
Show answer
0-10) 1.8 10-15) 2.4 15-25) 1.5 25-45) 0.4
3

The frequency densities for the times, t minutes, that 80 customers waited in a post office queue are shown in the table.

Time (t minutes)Frequency density
0 < t ≤ 102
10 < t ≤ 301.5
30 < t ≤ 403

Mia says, "The 0 < t ≤ 10 class must have the most customers because its bar is tall." Is Mia correct? You must show your working.

2 marks
Show answer
No: 0-10 has 20 customers, 10-30 has 30, 30-40 has 30. The 0-10 class has the fewest.
4

A histogram is drawn to show the masses, m grams, of some plums. The vertical axis has no scale, so the table records the height of each bar in centimetres.

Mass (m grams)Bar height (cm)
20 < m ≤ 306
30 < m ≤ 504.5
50 < m ≤ 558
55 < m ≤ 702

There are 24 plums with masses in the class 20 < m ≤ 30.

  1. Work out the number of plums in the class 30 < m ≤ 50.
  2. Work out the total number of plums.
010203040506070Mass (grams)Frequency density
4 marks
Show answer
a) 36 b) 88
5

The table shows information about the ages, a years, of the people at a village fete.

Age (a years)FrequencyFrequency density
0 < a ≤ 10303
10 < a ≤ 30f
30 < a ≤ 60451.5
  1. Write an expression, in terms of f, for the frequency density of the class 10 < a ≤ 30.
  2. The bar for this class is drawn 1.8 units high. Work out the value of f.
3 marks
Show answer
a) f/20 b) 36
6

The table and histogram give information about the distances, d km, that some students travel to college.

Distance (d km)Frequency
0 < d ≤ 416
4 < d ≤ 6
6 < d ≤ 1018
10 < d ≤ 16

The bars for 0 < d ≤ 4 and 4 < d ≤ 6 are already drawn on the histogram. The bar for 4 < d ≤ 6 has frequency density 5.5.

  1. Use the histogram to work out the frequency for 4 < d ≤ 6.
  2. The frequency for 10 < d ≤ 16 is 9. Complete the histogram.
02468101214160123456Distance (km)Frequency density
4 marks
Show answer
a) 11 b) bar height 4.5 over 6-10 and bar height 1.5 over 10-16
7

200 people were asked how long their journey to work takes. The table shows some of the results.

Time (t minutes)FrequencyFrequency density
0 < t ≤ 10404
10 < t ≤ 30603
30 < t ≤ 40
40 < t ≤ 60

25% of the people take more than 30 minutes and up to 40 minutes. All the remaining people are in the last class.

  1. Work out the frequency density for 30 < t ≤ 40.
  2. Work out the frequency density for 40 < t ≤ 60.
4 marks
Show answer
a) 5 b) 2.5
8

A histogram shows the times, t seconds, that 60 shoppers waited at a checkout. The table gives the frequency densities.

Time (t seconds)Frequency density
0 < t ≤ 200.6
20 < t ≤ 302.0
30 < t ≤ 353.2
35 < t ≤ 500.8
  1. Show that the histogram represents 60 shoppers.
  2. One of the 60 shoppers is chosen at random. Work out an estimate for the probability that this shopper waited more than 40 seconds.
4 marks
Show answer
a) 12 + 20 + 16 + 12 = 60 b) 2/15 (8/60)
9

The table shows the frequency densities for the times, t seconds, that a number of pupils took to run 100 m. A pie chart is to be drawn to show the same information.

Time (t seconds)Frequency density
10 < t ≤ 200.8
20 < t ≤ 302.4
30 < t ≤ 501.1
50 < t ≤ 700.3

Work out the angle of the sector of the pie chart for the class 30 < t ≤ 50.

3 marks
Show answer
132
10

The table shows the distances, d km, cycled by 64 members of a cycling club one Sunday.

Distance (d km)Frequency
0 < d ≤ 510
5 < d ≤ 1530
15 < d ≤ 208
20 < d ≤ 4016
  1. On the grid, draw a histogram for this information.
  2. Explain why 5 < d ≤ 15 is the modal class even though 20 < d ≤ 40 has a wider bar.
01020304000.511.522.533.5Distance (km)Frequency density
4 marks
Show answer
a) bar heights 2, 3, 1.6, 0.8 b) Frequency density (bar height), not bar width, identifies the modal class; 5 < d <= 15 has the highest frequency density
11

The table shows the masses, m kg, of 50 lambs on a farm. A histogram is to be drawn.

Mass (m kg)FrequencyFrequency density
40 < m ≤ 506
50 < m ≤ 6014
60 < m ≤ 6515
65 < m ≤ 8015
  1. Complete the frequency density column, to give the height of each bar.
  2. Use the table to estimate the median mass of the lambs. Give your answer correct to 3 significant figures.
5 marks
Show answer
a) 0.6, 1.4, 3, 1 b) 61.7
12

The histogram shows the masses, m kg, of the 40 dogs seen at a vet's surgery one week.

  1. Use the histogram to complete a frequency table for the four classes.
  2. Write down the class interval that contains the lower quartile of the masses.
  3. Work out an estimate for the number of dogs with a mass greater than 20 kg.
051015202530354000.511.522.5Mass (kg)Frequency density
5 marks
Show answer
a) 8, 12, 14, 6 b) 10 < m <= 15 c) 13
13

The table shows the speeds, s mph, of 60 vehicles passing a speed camera.

Speed (s mph)Frequency
0 < s ≤ 208
20 < s ≤ 3018
30 < s ≤ 4024
40 < s ≤ 6010
  1. On the grid, draw a histogram for this information.
  2. Work out an estimate for the fraction of the vehicles travelling at more than 35 mph. Give your fraction in its simplest form.
010203040506000.511.522.5Speed (mph)Frequency density
5 marks
Show answer
a) bar heights 0.4, 1.8, 2.4, 0.5 b) 11/30
14

120 students sat a test. The table shows the frequency densities for their marks, m.

Mark (m)Frequency density
0 < m ≤ 200.5
20 < m ≤ 401.5
40 < m ≤ 602
60 < m ≤ 702.5
70 < m ≤ 1000.5

The teacher awards a certificate to the top 10% of the students.

Estimate the lowest mark a student could get and still receive a certificate.

4 marks
Show answer
76
15

A gym has 200 members. A histogram shows the ages, a years, of the members. Some of the information is given in the table.

Age (a years)FrequencyFrequency density
0 < a ≤ 10303
10 < a ≤ 256
25 < a ≤ 45
45 < a ≤ 601
  1. Work out the frequency for the class 10 < a ≤ 25 and the frequency for the class 45 < a ≤ 60.
  2. Work out the frequency and the frequency density for the class 25 < a ≤ 45.
  3. Write down the class interval that contains the median age.
  4. Work out an estimate for the number of members older than 50.
6 marks
Show answer
a) 10 < a <= 25: 90; 45 < a <= 60: 15 b) frequency 65, frequency density 3.25 c) 10 < a <= 25 d) 10

Every question here is original and written by Robinson Tuition. The grade follows the Edexcel grade descriptors and suits AQA and OCR too; this is not an exam-board paper.

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