Multiplying by a one-digit number · Usually met around P3
×25 and ×125
Multiply 25 × 4 = 100 first.
How to do it
Method
Multiply 25 × 4 = 100 first
37 × 25 × 4 = 37 × 100 = 3700
Another way
Count four 25s
25, 50, 75, 100 → 37 × 100 = 3700
In full
When three numbers are multiplied, the order can change, so find the easy pair first: 25 × 4 = 100, 125 × 8 = 1000. 37 × 25 × 4 → first 25 × 4 = 100, then 37 × 100 = 3700: put two 0s after 37. 125 × 6 × 8 → 125 × 8 = 1000, 6 × 1000 = 6000. If you don't remember 25 × 4, count: 25, 50, 75, 100, so four 25s make 100; eight 125s are four 250s: 250, 500, 750, 1000. To check, work it again in another order.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
79 × 4 × 25
Show the answer and working
Answer: 79 × 4 × 25 = 7900
79 × 4 × 25: multiply the easy pair first, 25 × 4 = 100, then 79 × 100 = 7900
Example 2
4 × 25 × 25
Show the answer and working
Answer: 4 × 25 × 25 = 2500
4 × 25 × 25: multiply the easy pair first, 25 × 4 = 100, then 25 × 100 = 2500
Example 3
25 × 35 × 4
Show the answer and working
Answer: 25 × 35 × 4 = 3500
25 × 35 × 4: multiply the easy pair first, 25 × 4 = 100, then 35 × 100 = 3500
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