Page 32 - Maths Skills - 7

30 Maths

7. Find the reciprocal of the following:

7 18 5 3
(i) (ii) (iii) (iv) 2
9 7 19 5
3
8. Mr. Khanna’s monthly salary is ` 2400. If he spends of it, find the money spent by him.
4
3
9. Sylvy bought 6 m of cloth. She used th of the cloth for her dress. What length of cloth is used in her
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dress and what length was left with her?
10. Revati has 1.5 litres of apple juice. She gave one-fifth of this to each of her five friends. What quantity
is consumed by each of her friends?
11. In a school, one-third of the students go by bus, one-quarter of them walk to the school and the remaining
use their own conveyance. If the total number of students in the school is 2400, find the number of
students:
(i) going by bus (ii) walking to the school (iii) using own conveyance

DIVISION OF FRACTIONS
Division of a Whole Number by a Fraction
To divide a whole number by any fraction, multiply the whole number by the reciprocal of that fraction.

3 5 2  3 2
For example, 15 ÷ = 15 × = 5 × 2 = 10 Reciprocal of is
2 3  2 3  

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Similarly, to divide a whole number by a mixed fraction, first change the mixed fraction into an improper fraction
and then solve it.
2 17 5 30 13
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For example, 63÷ = 6÷ =× = = 1 .
5 5 17 17 17
Division of a Fraction by a Natural Number
To divide a fraction by natural number, multiply the fraction by the reciprocal of that natural number.
1
7 7 1 1
For example, ÷ 14 = × =
5 5 14 10
2
Similarly, to divide a mixed fraction by a natural number, convert the mixed fraction into an improper and then
solve it.
1 11 11 1 11
For example, 2 ÷ 10 = ÷ 10 = × =
5 5 5 10 50
Division of a Fraction by Another Fraction

To divide a fraction by another fraction, multiply the first fraction by the reciprocal of the second fraction.

7 2 7 5 35 Fact-o-meter
For example, ÷ = × =
3 5 3 2 6 � To divide any fraction by a natural number
6 or fraction, first multiply the fraction by
4 3 18 3 18 4 24 3
2 ÷ = ÷ = × = = 3 . the reciprocal of given number or fraction
7 4 7 4 7 3 7 7 and then solve it.
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� To do the division of fractions, change ‘÷’ to
‘×’ and write the reciprocal of the fraction.