tính nhẩm a.312×101 b.312×99 c169.101 d169x99

Đáp án:

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`a,`

`312 × 101`

`= 312 × (100 + 1)`

`= 312 × 100 + 312 × 1`

`= 31200 + 312`

`= 31512`

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`b,`

`312 × 99`

`= 312 × (100 – 1)`

`= 312 × 100 – 312 × 1`

`= 31200 – 312`

`= 30888`

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`c,`

`169 × 101`

`= 169 × (100 + 1)`

`= 169 × 100 + 169 × 1`

`= 16900 + 169`

`= 17069`

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`d,`

`169 × 99`

`= 169 × (100 – 1)`

`= 169 × 100 – 169 × 1`

`= 16900 – 169`

`= 16731`