Find a percentage in your head

Move the decimal point one place

To find 10% of a number, move the decimal point one place to the left. 10% of 60 is 6. 10% of 48 is 4.8.

Build other percentages from that piece. 30% is three of them; 5% is half of one.

One block in ten: 10% of 60 is 6.

60 × 0.1 = 6

6 × 3 + 3 = 21

To find 35% of 60, combine three 10% pieces and one 5% piece. Each 10% piece is 6, and the 5% piece is 3.

The numbers can also swap places: 4% of 75 equals 75% of 4, which is 3. Both calculations are 4 × 75 ÷ 100.

The 5% piece is half of the 10% piece, not the number 5. Half of 6 is 3.

Successive changes

Apply each percentage to the amount reached after the previous change. Opposite percentages do not cancel.

100 × 1.2 = 120; 120 × 0.8 = 96

Percentage points and change

Percentage points are the difference between rates. Percentage change divides that difference by the original rate, then multiplies by 100.

20% → 30%: 30 − 20 = 10

(30 − 20) ÷ 20 × 100 = 50%

Find the percentage

Divide the part by the whole, then multiply by 100.

18 ÷ 72 × 100 = 25%

Three and a half blocks: 35% of 60 is 21.

A bill comes to 48, and you want to leave a 15% tip.

Find 10% of 48 first, then add half of that.

One and a half blocks: 15% of 48.

What is 15% of 48?

Show the answer

7.20

10% of 48 is 4.80, and half of that is 2.40. Together they make 7.20.

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