Page 280 - Math Smart - 7

CHAPTER 12.2

In this chapter
Percentages in
Pupils should be able to:
• calculate simple
percentages of
quantities (whole Quantities
number answers)
• express a smaller
quantity as a fraction or
Investigate!
percentage of a larger
one
• use percentages to Look at the notice that was on display at a local shop.
represent and compare
different quantities

^ RECALL

O Find the value of each
of the following.

a) 27% of 450
b) 81% of 96

c) 36% of
1250 m m
What is wrong with the notice?
d) 74% of
65^
12.2.1 Finding the percentage of
0 Mrs Singh had $2400.
She spent ^ of her 0 quantity
money on a printer
and 28% of her money To find a percentage of an amount, first write the percentage as a fraction.
on a wardrobe. How Then multiply the fraction by that amount.
much money does she
have left? Example 1

Find the following values,
a) 3% of 200 b) 24% of 400 c) 5% of 20 d) 70% of 285

Solution
Take the whole
Method 1
number as 100%.
a) 100% 200 b) 100%-^400
200 ^
1% Find 1% 1% ^ =4 Find 1%
^
100 "
3%' 2x3 = 6 Multiply by 3 24% -► 4 X 24 = 96 Multiply by 24
3% of 200 = 6 24% of 400 = 96
UNIT 12 I Percentages