Multiply decimals
2.4 x 3 means 24 tenths x 3 = 72 tenths, which is 7.2.
The answer should stay close to the estimate.
Year 6
Multiply one-digit numbers with up to two decimal places by whole numbers and use written division methods in cases where the answer has up to two decimal places
Calculate with decimals using clear place-value reasoning and written methods.
Lesson overview
Number - fractions, decimals and percentages
Decimal calculations work like whole-number calculations when place value is kept aligned. A quick estimate helps check whether the decimal answer is sensible.
Divide decimals
4.8 ÷ 4 = 1.2.
Think about sharing tenths equally.
Worked example
Work out 3.6 x 4.
| Estimate | Exact |
|---|---|
| about 4 x 4 = 16 | 14.4 |
- Estimate first: 3.6 is close to 4, so the answer should be near 16.
- Multiply 36 tenths by 4 to get 144 tenths.
- 144 tenths is 14.4.
- So 3.6 x 4 = 14.4.
Try it
Estimate first so you know roughly how large the decimal answer should be.
Question 1
2.4 x 3 =
Question 2
4.8 ÷ 4 =
Question 3
3.6 x 4 =
Question 4
Which answer is sensible for 1.25 x 6?
Question 5
7.2 ÷ 6 =
Common mistakes
Watch for these when working through the lesson.
- Dropping the decimal part and giving a whole-number answer.
- Placing the decimal point in the wrong place.
- Ignoring whether the answer should be greater or smaller than the starting number.
Related topics
These ideas fit closely with this lesson.
- Identify the value of each digit in numbers given to three decimal places.
- Use estimation to check answers to calculations.