Contents

## Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling

**Selina Publishers Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling**

### Data Handling Exercise 21A – Selina Concise Mathematics Class 7 ICSE Solutions

**Question 1.**

**Consider the following numbers :**

** 68, 76, 63, 75, 93, 83, 70, 115, 82, 105, 90, 103, 92, 52, 99, 73, 75, 63, 77 and 71.**

** (i) Arrange these numbers in ascending order.**

** (ii) What the range of these numbers?**

**Solution:**

**Question 2.**

**Represent the following data in the form of a frequency distribution table :**

** 16, 17, 21, 20, 16, 20, 16, 18, 17, 21, 17, 18, 19, 17, 15, 15, 19, 19, 18, 17, 17, 15, 15, 16, 17, 17, 19, 18, 17, 16, 15, 20, 16, 17, 19, 18, 19, 16, 21 and 17.**

**Solution:**

**Question 3.**

**A die was thrown 20 times and following scores were recorded.**

** 2, 1, 5, 2, 4, 3, 6, 1, 4, 2, 5, 1, 6, 2, 6, 3, 5, 4, 1 and 3.**

** Prepare a frequency table for the scores.**

**Solution:
**

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**Question 4.
**

**Following data shows the weekly wages (in ₹) of 10 workers in a factory.**

**3500, 4250, 4000, 4250, 4000, 3750, 4750, 4000, 4250 and 4000**

**(i) Prepare a frequency distribution table.**

**(ii) What is the range of wages (in ₹)?**

**(iii) How many workers are getting the maximum wages?**

**Solution:**

**Question 5.
**

**The marks obtained by 40 students of a class are given below :**

**80, 10, 30, 70, 60, 50, 50, 40, 40, 20, 40, 90, 50, 30, 70, 10, 60, 50, 20, 70, 70, 30, 80, 40,20, 80, 90, 50, 80, 60, 70, 40, 50, 60, 90, 60, 40, 40, 60 and 60**

**(i) Construct a frequency distribution table.**

**(ii) Find how many students have marks equal to or more than 70?**

**(iii) How many students obtained marks below 40?**

**Solution:**

**Question 6.
**

**Arrange the following data in descending order:**

**3.3, 3.2, 3.1, 3.7, 3.6, 4.0, 3.5, 3.9, 3.8, 4.1, 3.5, 3.8, 3.7, 3.9 and 3.4.**

**(i) Determine the range.**

**(ii) How many numbers are less than 3.5?**

**(iii) How many numbers are 3.8 or above?**

**Solution:**

### Data Handling Exercise 21B – Selina Concise Mathematics Class 7 ICSE Solutions

**Question 1.**

**Find the mean of 53, 61, 60, 67 and 64.**

**Solution:
**

**Question 2.
**

**Find the mean of first six natural numbers.**

**Solution:**

**Question 3.
**

**Find the mean of first ten odd natural numbers.**

**Solution:**

**Question 4.
**

**Find the mean of all factors of 10.**

**Solution:**

**Question 5.
**

**Find the mean of x + 3, x + 5, x + 7, x + 9 and x + 11.**

**Solution:**

**Question 6.
**

**If different values of variable x are 19.8,15.4,13.7,11.71,11.8, 12.6,12.8,18.6,20.5 and 2.1, find the mean.**

**Solution:**

**Question 7.
**

**The mean of a certain number of observations is 32. Find the resulting mean, if each observation is,**

**(i) increased by 3**

**(ii) decreased by 7**

**(iii) multiplied by 2**

**(iv) divided by 0.5**

**(v) increased by 60%**

**(vi) decreased by 20%**

**Solution:**

**Question 8.**

**The pocket expenses (per day) of Anuj, during a certain week, from monday to Saturday were ₹85.40, ₹88.00, ₹86.50, ₹84.75, ₹82.60 and ₹87.25. Find the mean pocket expenses per day.**

**Solution:
**

**Question 9.
**

**If the mean of 8, 10, 7, x + 2 and 6 is 9, find the value of x.**

**Solution:**

**Question 10.
**

**Find the mean of first six multiples of 3.**

**Solution:**

**Question 11.
**

**Find the mean of first five prime numbers.**

**Solution:**

**Question 12.
**

**The mean of six numbers :x-5,x- 1, x, x + 2, x + 4 and x + 12 is 15. Find the mean of first four numbers.**

**Solution:**

**Question 13.
**

**Find the mean of squares of first five whole numbers.**

**Solution:**

**Question 14.
**

**If the mean of 6, 4, 7, p and 10 is 8, find the value of p.**

**Solution:**

**Question 15.
**

**Find the mean of first six multiples of 5.**

**Solution:**

**Question 16.
**

**The rainfall (in mm) in a city on 7 days of a certain week is recorded as follows**

**Find the total and average (mean) rainfall for the week.**

**Solution:**

**Question 17.
**

**The mean of marks scored by 100 students was found to be 40, later on it was discovered that a score of 53 was misread as 83. Find the correct mean.**

**Solution:**

**Question 18.
**

**The mean of five numbers is 27. If one number is excluded, the mean of remaining numbers is 25. Find the excluded number.**

**Solution:**

**Question 19.
**

**The mean of 5 numbers is 27. If one new number is included, the new mean is 25. Find the included number.**

**Solution:**

**Question 20.**

**Mean of 5 numbers is 20 and mean of other 5 numbers is 30. Find the mean of all the 10 numbers taken together.**

**Solution:
**

**Question 21.
**

**Find the median of:**

**(i) 5,7, 9, 11, 15, 17,2, 23 and 19**

**(ii) 9, 3, 20, 13, 0, 7 and 10**

**(iii) 18, 19, 20, 23, 22, 20, 17, 19, 25 and 21**

**(iv) 3.6, 9.4, 3.8, 5.6, 6.5, 8.9, 2.7, 10.8, 15.6, 1.9 and 7.6.**

**Solution:**

**Question 22.**

**Find the mean and the mode for the following data :**

**Solution:
**

**Question 23.
**

**Find the mode of:**

**(i) 5, 6, 9, 13, 6, 5, 6, 7, 6, 6, 3**

**(ii) 7, 7, 8, 10, 10, 11, 10, 13, 14**

**Solution:**

**Question 24.
**

**Find the mode of :**

**Solution:**

**Question 25.
**

**The heights (in cm) of 8 girls of a class are 140,142,135,133,137,150,148 and 138 respectively. Find the mean height of these girls and their median height.**

**Solution:**

**Question 26.
**

**Find the mean, the median and the mode of:**

**(i) 12, 24, 24, 12, 30 and 12**

**(ii) 21, 24, 21, 6, 15, 18, 21, 45, 9, 6, 27 and 15.**

**Solution:**

**Question 27.**

**The following table shows the market positions of some brands of soap.**

** Draw a suitable bar graph :**

**Solution:**

**Question 28.**

**The birth rate per thousand of different countries over a particular period of time is shown below.**

**Solution:**