NCERT Class 7 Mathematics

(Ron) #1
FRACTIONS AND DECIMALS 39

The value of
1
3
×
1
2
can be found in a similar way. Divide the whole into two equal

parts and then divide one of these parts in three equal parts. Take one of these parts. This


will represent^1
3 ×


1
2 i.e.,

1
6

.

Therefore
1
3
×
1
2


1
6


11
32




as discussed earlier.

Hence
1
2
×
1
3


1
3
×
1
2


1
6


Find
1
3
×
1
4
and
1
4
×
1
3
;
1
2
×
1
5
and
1
5
×
1
2
and check whether you get


1
3 ×

1
4 =

1
4 ×

1
3 ;

1
2 ×

1
5 =

1
5 ×

1
2

Fill in these boxes:

(i)
1
2 ×

1
7 =

11
27


 = (ii)

1
5 ×

1
7 = =

(iii)

1
7 ×

1
2 = = (iv)

1
7 ×

1
5 = =

Example 6 Sushant reads


1
3 part of a book in 1 hour. How much part of the book
will he read in 21
5

hours?

SOLUTION The part of the book read by Sushant in 1 hour =
1
3
.


So, the part of the book read by him in
21
5
hours =
21
5
×
1
3


11
5
×
1
3


 


11 1
53
=
11
15

Let us now find
1
2
×
5
3


. We know that
5
3
=
1
3
× 5.


So,

1
2 ×

5
3 =

1
2 ×

1
3 × 5 =

1
6

5 5
6



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