Page 76 - Math Skill - 5

74 Maths

13
3. The cost of one pen is ` 15 . What is the cost of 15 such pens?
20
3
4. An iron rod has been cut into 8 pieces of equal length. If the length of each piece is 5 m,
4
what was the original length of the iron rod?

4
5. One litre of petrol costs ` 68 . What is the cost of 37 litres of petrol?
5
3
6. Find the area of a square of each side 7 metres.
4
7. A test was given to a class of 42 students. If 5 of these students passed, then how
many failed? 6
3
8. The capacity of a parking place is of 90 cars. At a particular time, of the parking place
is occupied. How many more cars can be parked at that time? 5

Division of Fractions

To understand the concept of division of fractions, we must first understand the concept of
multiplicative inverse, also called reciprocal.
Two numbers are reciprocal to each other if their product is 1.
1 1
For example, 3 and are reciprocal to each other because 3 × = 1.
3 3
3
3
4
Similarly, the reciprocal of is as × 4 = 1
Fact-o-meter
4 3 4 3 � To find the reciprocal of proper or
1
The reciprocal of 2 is 5 improper fractions, interchange the
5 11 numerator and denominator.
1 5 11 5 � The reciprocal of 1 is 1 itself.
as 2 × = × = 1. � 0 does not have any reciprocal.
5 11 5 11

Let’s Attempt

Example 1: Find the reciprocal of:

1 2
(a) 1 (b) 6 (c) (d) 1
4 11

1
Solution: (a) 1 = 5
4 4
5 4  5 4 
The reciprocal of is .   × = 1 
4 5  4 5 

1
(b) The reciprocal of 6 is .   6 × 1 = 1 
6  1 6 


2 11
(c) The reciprocal of is .  2 11 
11 2   11 × 2 = 1 


(d) The reciprocal of 1 is 1.