Chapter 4 ยท ICSE Class 5 Math

Percentages

A percentage is just a fraction out of 100 โ€” you already know this idea from decimals. Drag the slider and watch the grid fill up to see it directly.

The Percent Machine
45%
= 45/100 = 0.45
45%

Try it: set the slider to 50 โ€” that's the same as one half.

A pie chart showing 25 percent shaded A circle with one quarter shaded to represent 25 percent of the whole 25%
4.1

What is a percentage?

"Per cent" means "out of 100." A percentage is just a special way of writing a fraction with denominator 100 โ€” instead of writing 45/100, we write 45%. You already know how to write this as a decimal too: 45% = 0.45.

Everyday example โ€” A "50% off" sale means the price drops by half โ€” because 50% is the same as 50/100, which simplifies to 1/2. Try setting the Percent Machine above to 50 to see the grid exactly half filled.
4.2

Converting between forms

Percentage
25%

Read as "25 per cent."

Fraction
25/100 = ยผ

Divide by 100, then simplify.

Decimal
0.25

Move the decimal point two places left.

4.3

Comparing percentages

1Direct comparison

Since percentages are all "out of 100," you can compare them directly, just like whole numbers. 65% is bigger than 40%.

2Comparing a percentage and a fraction

Is 3/5 bigger than 55%? Convert 3/5 to a percentage: 3/5 = 60/100 = 60%.

60% is bigger than 55%, so 3/5 is bigger.

4.4

Finding a percentage of a quantity

1Finding 10% first

Find 10% of โ‚น250. 10% means dividing by 10.

10% of 250 = 25

2Building up from 10%

Find 30% of โ‚น250. Since 30% = 3 ร— 10%, and 10% of 250 is 25:

30% of 250 = 3 ร— 25 = 75

3A class of students

A class has 40 students. If 25% of them play chess, how many students is that?

25% = ยผ, so ยผ of 40 = 10 students

Watch out โ€” "Percentage of a quantity" means multiply, not just write the percent sign next to the number. 20% of 50 is 10 โ€” not "20" and not "50%."
๐ŸŽฎ Percentage City

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