108
Percent
Textbook: Part 3, lesson 108, pp. 114–115
GoalPercent: one hundredth of a number; finding 100%, 50%, 25%, 10% and 1%.
New words
percent · foizone hundredth · yuzdan birhalf · yarimquarter · chorak
Explanation
One hundredth of a number is called a percent. 1% = 1/100 = 0.01. Every number is 100% of itself. To find a percent, find one hundredth of the number and multiply by the number of percent. Easy cases: 50% is a half (1/2), 25% is a quarter (1/4), 10% is a tenth (1/10), 1% is a hundredth. For example 50% of 600 = 300, 25% of 80 = 20.
Worked examples
43% = 43/100; 9/100 = 9%.
25% of 160 pupils: 160 : 4 = 40 pupils.
Class activity
“Percent square”: in a 100-square grid, children colour 50, 25 and 10 squares and say what percent each is.
Practice
1
Write 43% as hundredths.
43/100
2
Write 9/100 as a percent.
9%
3
Find 25% of 80.
20
4
Find 50% of 500.
250
5
A library has 240 books. 25% of them are fairy-tale books. How many fairy-tale books are there?
60
6
Find 10% of 300.
30