Page 48 - Math 7

Operations on Whole Numbers

Example 4: Simplify a) 8 × 2 18 × 3 75 (b) 144
441
Solution:
a) 8 × 2 18 × 3 75
Think of the factors of 8, 18 and 75 such
= 4 × 2 × 2 9 × 2 × 3 25 × 3 that one of the factors is a perfect square.

= 2 2 × 2 × 3 2 × 3 × 5 3 Find the square root of each perfect square factor.

= 180 12 2 × 6 × 15 = 180 and 2 × 2 × 3 = 12

= 180 × 4 × 3 Think of the factors of 12 such that one of
the factors is a perfect square.
= 180 u 2 3
= 360 3
144 = 2 × 2 × 2 × 2 × 3 × 3
2
2
2
2
b) 144 = 2 × 2 × 3 2 = 2 × 2 × 3 2
2
2
441 3 × 7 441 = 3 × 3 × 7 × 7
2
= 2 × 2 = 4 = 3 × 7 2
7 7
Example 5: Find the square root of 3.24
Solution:
2 324 2 100
Here, 3.24 = 324 2 162 2 50
100
3 81 5 25
? 3.24 = 324 3 27 5
100
3 9
2 × 3 × 3 2 3
2
2
= 2 × 5 2 324 = 2 × 2 × 3 × 3 × 3 × 3
2
2
2
= 2 × 3 × 3 = 2 × 3 × 3 2
2 × 5 100 = 2 × 2 × 5 × 5
2
= 18 = 1.8 = 2 × 5 2
10
Example 6 : There are 40 pupils in class 7. If every pupil collects as much as
money as their numbers for a charity show, how much money do
they collect altogether?
Solution:
Here, Number of pupils = 40
sum of money collected from each pupil = Rs 40
Thus, the required sum of money = Rs (40 )
2
= Rs ( 40 × 40) = Rs 1600.
Hence, they collect Rs 1,600 altogether.

Vedanta Excel in Mathematics - Book 7 46 Approved by Curriculum Development Centre, Sanothimi, Bhaktapur