Why the trick works
25 is one fourth of 100. That means multiplying by 25 is the same as multiplying by 100 and dividing by 4.
Use it when the number divides by 4
If the number is divisible by 4, divide first and then multiply by 100. Example: 48 x 25. Since 48 / 4 = 12, the answer is 1200.
Use splitting for awkward numbers
If the number is not easy to divide by 4, split it into friendly pieces. Example: 58 x 25 = 40 x 25 + 18 x 25 = 1000 + 450 = 1450.
Practice problems
- 48 x 25
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Multiply by 100, then divide by 4. 4800 / 4 = 1200.
- 36 x 25
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3600 / 4 = 900.
- 34 x 25
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Split it as 30 x 25 + 4 x 25 = 750 + 100 = 850.
References
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