Multiplying decimals
You learn to do a whole number times a decimal, like 4 × 0.5.
How to work it out
- Remove the decimal point: 0.25 is 25 hundredths.
- Multiply with whole numbers.
- Put the decimal point back: 100 hundredths is 1.
A worked example
3 × 0.25
- Take the decimal point away: 0.25 is 25 hundredths.
- Work it out: 3 × 25 = 75.
- Put the decimal point back: 75 hundredths is 0.75.
More examples
4 × 0.5
- Take the decimal point away: 0.5 is 50 hundredths.
- Work it out: 4 × 50 = 200.
- Put the decimal point back: 200 hundredths is 2.
5 × 0.2
- Take the decimal point away: 0.2 is 20 hundredths.
- Work it out: 5 × 20 = 100.
- Put the decimal point back: 100 hundredths is 1.
Try it yourself
3 × 0.25 =
3 × 0.5 =
Watch out
You leave the decimal point in the same place: 4 × 0.5 becomes 0.20.
Check whether it makes sense: 0.5 is a half, and 4 halves are 2 wholes.
You count 0.5 as 5 hundredths: 4 × 0.5 becomes 0.2.
0.5 is 50 hundredths. Write it as 0.50 before you take the decimal point away.
Tips
- Count the digits after the decimal point: move the point back that many places.
Why it works
0.25 is 25 hundredths. You already know how to multiply by 25, and then you know how many hundredths it is. At the end you put the decimal point back.