RS Aggarwal 2019,2020 solution class 7 chapter 3 Decimals Exercise 3B

Exercise 3B

Page-41

Question 1:

Add:

16, 8.7, 0.94, 6.8 and 7.77

Answer 1:

Converting the given decimals into like decimals, we get:
16.00, 8.70, 0.94, 6.80 and 7.77
Writing these decimals in column form and adding, we get:

Hence, the sum of the given decimals is 40.21

Question 2:

Add:

18.6, 206.37, 8.008, 26.4 and 6.9

Answer 2:

Converting the given decimals into like decimals, we get:
18.600, 206.370, 8.008, 26.400 and 6.900
Writing these decimals in column form and adding, we get:

Hence, the sum of the given decimals is 266.278.

Question 3:

Add:

63.5, 9.7, 0.8, 26.66 and 12.17

Answer 3:

Converting the given decimals into like decimals, we get:
63.50, 9.70, 0.80, 26.66 and 12.17
Writing these decimals in column form and adding, we get:

Hence, the sum of the given decimals is 112.83.

Question 4:

Add:

17.4, 86.39, 9.435, 8.8 and 0.06

Answer 4:

Converting the given decimals into like decimals, we get:
17.400, 86.390, 9.435, 8.800 and 0.060
Writing these decimals in column form and adding, we get:

Hence, the sum of the given decimals is 122.085.

Question 5:

26.9, 19.74, 231.769 and 0.048

Answer 5:

Converting the given decimals into like decimals, we get:
26.900, 19.740, 231.769 and 0.048
Writing these decimals in column form and adding, we get:

Hence, the sum of the given decimals is 278.457.

Question 6:

Add:

23.8, 8.94, 0.078 and 214.6

Answer 6:

Converting the given decimals into like decimals, we get:
23.800, 8.940, 0.078 and 214.600
Writing these decimals in column form and adding, we get:

Hence, the sum of the given decimals is 247.418.

Question 7:

Add:

6.606, 66.6, 666, 0.066, 0.66

Answer 7:

Converting the given decimals into like decimals, we get:
6.606, 66.600, 666.000, 0.066 and 0.660
Writing these decimals in column form and adding, we get:

Hence, the sum of the given decimals is 739.932.

Question 8:

Add:

9.09, 0.909, 99.9, 9.99, 0.099

Answer 8:

Converting the given decimals into like decimals, we get:
9.090, 0.909, 99.900, 9.990 and 0.099
Writing these decimals in column form and adding, we get:

Hence, the sum of the given decimals is 119.988.

Question 9:

Subtract:

14.79 from 72.43

Answer 9:

The given decimals are like decimals. Writing them in column form with the larger one at the top and subtracting them, we get:

∴ (72.43 − 14.79) = 57.64

Question 10:

Subtract:

36.74 from 52.6

Answer 10:

Converting the given decimals into like decimals, we get:
36.74 and 52.60
Writing them in column form with the larger one at the top and subtracting them, we get:

∴ (52.60 − 36.74) = 15.86

Question 11:

Subtract:

13.876 from 22

Answer 11:

Converting the given decimals into like decimals, we get:
13.876 and 22.000
Writing them in column form with the larger one at the top and subtracting them, we get:

∴ (22.000 − 13.876) = 8.124

Question 12:

Subtract:

15.079 from 24.16

Answer 12:

Converting the given decimals into like decimals, we get:
15.079 and 24.160
Writing them in column form with the larger one at the top and subtracting them, we get:

∴ (24.160 − 15.079) = 9.081

Question 13:

Subtract:

0.68 from 1.007

Answer 13:

Converting the given decimals into like decimals, we get:
0.680 and 1.007
Writing them in column form with the larger one at the top and subtracting them, we get:

∴ (1.007 − 0.680) = 0.327

Question 14:

Subtract:

0.4678 from 5.05

Answer 14:

Converting the given decimals into like decimals, we get:
0.4678 and 5.0500
Writing them in column form with the larger one at the top and subtracting them, we get:

∴ (5.0500 − 0.4678) = 4.5822

Question 15:

Subtract:

2.5307 from 8

Answer 15:

Converting the given decimals into like decimals, we get:
2.5307 and 8.0000
Writing them in column form with the larger one at the top and subtracting them, we get:

∴ (8.0000 − 2.5307) = 5.4693

Question 16:

Subtract:

6.732 from 9.001

Answer 16:

Writing the given like decimals in column form with the larger one at the top and subtracting them, we get:

∴ (9.001 − 6.732) = 2.269

Question 17:

Take out 5.746 from 9.1.

Answer 17:

Converting the given decimals into like decimals, we get:
5.746 and 9.100
Writing them in column form with the larger one at the top and subtracting them, we get:

∴ (9.100 − 5.746) = 3.354

Question 18:

What is to be added to 63.58 to get 92?

Answer 18:

Converting the given decimals into like decimals, we get:
63.58 and 92.00
Thus, required number = (92.00 − 63.58) = 28.42
Hence, 28.42 should be added to 63.58 to get 92.

Question 19:

What is to be subtracted from 8.1 to get 0.813?

Answer 19:

Converting the given decimals into like decimals, we get:
8.100 and 0.813
Thus, required number = (8.100 − 0.813) = 7.287
Hence, 7.287 should be subtracted from 8.1 to get 0.813.

Question 20:

By how much should 32.67 be increased to get 60.1?

Answer 20:

Converting the given decimals into like decimals, we get:
32.67 and 60.10
Thus, required number = (60.10 − 32.67) = 27.43
Hence, 32.67 should be increased by 27.43 to get 60.1.

Question 21:

By how much should 74.3 be decreased to get 26.87?

Answer 21:

Converting the given decimals into like decimals, we get:
74.30 and 26.87
Thus, required number = (74.30 − 26.87) = 47.43
Hence, 74.3 should be decreased by 47.43 to get 26.87.

Question 22:

Rohit purchased a notebook for Rs 23.75, a pencil for Rs 2.85 and a pen for Rs 15.90. He gave a 50-rupee note to the shopkeeper. What amount did he get back?

Answer 22:

Total amount spent by Rohit on purchasing of the given articles = Rs (23.75 + 2.85 + 15.90)
                                                                                                 = Rs 42.50
Money given to the shopkeeper = Rs 50
∴ Money returned by the shopkeeper = Rs (50 − 42.50)
                                                          = Rs 7.50
Thus, amount received by Rohit = Rs 7.50