Example | Mental calculation | Reason | ||||||
398*4 | 1600-8=1592 |
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240*5 |
120*10 divide by 2 and multiply by 10 |
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320/5 |
640/10 multiply by 2 and divide by 10 |
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760*200 | calculate 76*2 and multiply by 1000 |
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12*25 |
3*100 divide by 4 and multiply by 100 |
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13*99 | 1300-13 |
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