To multiply decimals, multiply as whole numbers and then count the decimal places. 2.5 × 1.6: 25 × 16 = 400. There are two decimal places in total, so the answer is 4.00, which is 4.
To divide by a decimal, multiply both numbers by 10, 100 or 1000 so the divisor becomes a whole number. 7.2 ÷ 0.08 becomes 720 ÷ 8 = 90. Check every answer with an estimate.
Money and measurement problems often need these skills, such as finding the cost of 2.5 kg of apples at $1.60 per kilogram.
Worked example
3.4 × 1.5 =
- 34 × 15 = 510.
- Two decimal places in total: 5.10.
Answer:5.1
Key words
- decimal places
- digits after the point
- divisor
- the number you divide by
- estimate
- a rounded check
Practise this
New questions every time.
Common Core-referenced: 6.NS.B.3