Multiplying and dividing by two digits; divisibility · Usually met around P4
×5 by halving
×5 is ×10, then halve.
How to do it
Method
×5 is ×10, then halve
48 × 5 = 480 ÷ 2 = 240
Another way
Column multiplication
Ones 8 × 5 = 40, write 0, carry 4; tens 4 × 5 + 4 = 24 → 240
In full
×5 is ×10, then halve. 48 × 5 → 480 → 240. It works for odd numbers too: 37 × 5 → 370 → 185. Same idea: ×50 is ×100 halved, and ×25 is ×100 divided by 4. You can also multiply in columns.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
15 × 5
Show the answer and working
Answer: 15 × 5 = 75
15 × 5: ×5 is ×10 then halved, 15 × 10 = 150, 150 ÷ 2 = 75
Example 2
71 × 5
Show the answer and working
Answer: 71 × 5 = 355
71 × 5: ×5 is ×10 then halved, 71 × 10 = 710, 710 ÷ 2 = 355
Example 3
67 × 5
Show the answer and working
Answer: 67 × 5 = 335
67 × 5: ×5 is ×10 then halved, 67 × 10 = 670, 670 ÷ 2 = 335
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