RS Aggarwal Solutions: Decimals (Exercise 3B) | Mathematics (Maths) Class 7 PDF Download

Q.1. Add: 16, 8.7, 0.94, 6.8 and 7.77
Ans. 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

Q.2. Add: 18.6, 206.37, 8.008, 26.4 and 6.9
Ans. 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.

Q.3. Add: 63.5, 9.7, 0.8, 26.66 and 12.17
Ans. 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.

Q.4. Add: 17.4, 86.39, 9.435, 8.8 and 0.06
Ans. 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.

Q.5. 26.9, 19.74, 231.769 and 0.048
Ans. 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.

Q.6. Add: 23.8, 8.94, 0.078 and 214.6
Ans. 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.

Q.7. Add: 6.606, 66.6, 666, 0.066, 0.66
Ans. 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.

Q.8. Add: 9.09, 0.909, 99.9, 9.99, 0.099
Ans. 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.

Q.9. Subtract: 14.79 from 72.43
Ans. 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

Q.10. Subtract: 36.74 from 52.6
Ans. 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

Q.11. Subtract: 13.876 from 22
Ans. 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

Q.12. Subtract: 15.079 from 24.16
Ans. 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

Q.13. Subtract: 0.68 from 1.007
Ans. 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

Q.14. Subtract: 0.4678 from 5.05
Ans. 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

Q.15. Subtract: 2.5307 from 8
Ans. 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

Q.16. Subtract: 6.732 from 9.001
Ans. 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

Q.17. Take out 5.746 from 9.1.
Ans. 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

Q.18. What is to be added to 63.58 to get 92?
Ans. 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.

Q.19. What is to be subtracted from 8.1 to get 0.813?
Ans. 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.

Q.20. By how much should 32.67 be increased to get 60.1?
Ans. 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.

Q.21. By how much should 74.3 be decreased to get 26.87?
Ans. 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.

Q.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?
Ans. 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