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Std 7 Mathematics · Chapter 15

15. Statistics

Step-by-step solutions to Practice Sets 54 and 55: average and frequency distribution tables with tally marks. Maharashtra State Board (Balbharati), Grade Seven Mathematics.

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Average = Sum of all scoresTotal number of scores

Practice Set 54

1The daily rainfall for each day of a week in a certain city is given in millimetres. Find the average rainfall during the week. 9, 11, 8, 20, 10, 16, 12

Average = 9 + 11 + 8 + 20 + 10 + 16 + 127 = 867 = 1227 ≈ 12.29

The average rainfall during the week is 1227 mm (about 12.29 mm).

2During the annual function of a school, a Women’s Self-help Group had set up a snacks stall. Their sales every hour were worth ₹ 960, ₹ 830, ₹ 945, ₹ 800, ₹ 847, ₹ 970 respectively. What was the average of the hourly sales?

Average = 960 + 830 + 945 + 800 + 847 + 9706 = 53526 = 892

The average hourly sale was ₹ 892.

3The annual rainfall in Vidarbha in five years is given below. What is the average rainfall for those 5 years? 900 mm, 650 mm, 450 mm, 733 mm, 400 mm

Average = 900 + 650 + 450 + 733 + 4005 = 31335 = 626.6

The average annual rainfall is 626.6 mm.

4A farmer bought some sacks of animal feed. The weights of the sacks are given below in kilograms. What is the average weight of the sacks? 49.8, 49.7, 49.5, 49.3, 50, 48.9, 49.2, 48.8

Number of sacks = 8
Average = 49.8 + 49.7 + 49.5 + 49.3 + 50 + 48.9 + 49.2 + 48.88 = 395.28 = 49.4

The average weight of a sack is 49.4 kg.

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Practice Set 55

Write the scores in ascending order, put a tally mark for each score as you read the data (every fifth mark is drawn across the first four), count the marks to get the frequency, and check that the total frequency N equals the number of scores.

1The height of 30 children in a class is given in centimetres. Draw up a frequency table of this data.
Height (cm)Tally marksFrequency
131|||3
132|||3
133||||5
134|||3
135|||3
136||2
137||2
138|1
139|||3
140||||5
Total frequencyN = 30

The most common heights are 133 cm and 140 cm (5 children each).

2In a certain colony, there are 50 families. The number of people in every family is given below. Draw up the frequency table.
Number of peopleTally marksFrequency
1|1
2|||||||||||13
3|||||||||||||16
4|||||||||||13
5||||||7
Total frequencyN = 50
3A dice was cast 40 times and each score noted is given below. Draw up a frequency table for this data.
Score on the diceTally marksFrequency
1||2
2|||||||8
3|||||||||||13
4|||||||8
5||||5
6||||4
Total frequencyN = 40
4The number of chapatis that 30 children in a hostel need at every meal is given below. Make a frequency table for these scores.
Number of chapatisTally marksFrequency
2||||||||9
3||||||||10
4|||||||8
5|||3
Total frequencyN = 30
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