Exercise 3.1
1. Write each of the following as decimals:
(i) 8/100
Solution:
Mark the decimal point two places from right to left
Mark the decimal point one place from right to left
9/10 = 0.9
4/100
Mark the decimal point two places from right to left
4/100
= 0.04
= 20 + 0.9+ 0.04
= 20.94
Solution:
Convert 2/10 and 6/1000 into decimals
2/10
Mark the decimal point one place from right to left
2/10
= 0.2
6/1000
Mark the decimal point three places from right to left
6/1000
= 0.006
23, 0.2, 0.006 are unlike decimals. So we convert them into like decimals.
2. Convert each of the following into fractions in the lowest form:
(i) 0.04
Solution:
(ii) 2.34
Solution:
(iii) 0.342
Solution:
(iv) 17.38
Solution:
3. Express the following fractions as decimals:
(i) (23/10)
Solution:
Given (23/10)
Divide 23 by we get
(23/10) = 2.3
(ii) 25 (1/8)
Solution:
Given 25 (1/8)
25 (1/8) can be written as
25(1/8) = 25 + (1/8)
Consider (1/8)
Now multiply both numerator and denominator by 125 to get 1000 as denominator
25 (1/8) = 25+ (1/8) = 25 + (1×125/8×125)
= 25+ (125/1000)
= 25 + 0.125
= 25.125
(iii) 39 (7/35)
Solution:
Given 39 (7/35)
First convert given mixed fraction 39 (7/35) into fraction
39 (7/35) = 132/ 35
By dividing we get
39 (7/35) = 39.2
(iv) 15 (1/25)
Solution:
Given 15 (1/25)
15 (1/25) can be written as
15 (1/25) = 15 + (1/25)
Consider (1/25),
Now multiply both numerator and denominator by 4 to get 100 as denominator
15 (1/25) 15 + (1/25) = 15 + (1×4/25×4)
= 15+ (4/100)
= 15 + 0.004
= 15. 04
4. Add the following:
(i) 41.8, 39.24, 5.01 and 62.6
Solution:
148.65
(ii) 18.03, 146.3, 0.829 and 5.324
Solution:
170.483
5. Find the value of:
(i) 9.756 – 6.28
(ii) 48.1- 0.37
(iii) 108.032 – 86.8
(iv) 100 – 26.32
Answer:
(i) 3.476
(ii) 47.73
(iii) 21.232
(iv) 73.68
6. Take out 3.547 from 7.2
Solution:
3.653
7. What is to be added to 36.85 to get 59.41?
Solution:
Given 36.85 and 5941
Let the unknown number x
X + 36.85 = 59.41
X = 36.85 = 59.41
X = 59.41- 36.85
X = 22.56
Then, 22.56 is to be added to 36.85 to get 59.41
8. What is to subtracted from 17.1 to get 2.051?
Solution:
Let the unknown number x
Given that x to be subtracted from 17.1 get 2.051
17.1 – x = 2.051
17.1 – 2.051 = x
X = 17.1- 2.051
X = 15.049
9. By how much should 34.79 be increased to get 70.15?
Solution:
34.79 + x = 70.15
x = 70.15 – 34.79
x = 35.36
Then, 35.36 is increased to 70.15
10. By how much should 59.71 be decreased to get 34.58?
Solution:
59.71 – x = 34.58
59.71 – 34.58 = x
x = 25.13
Then, 25.13 is decreased to get 34.58