Question

79×3.9+3.9脱式计算

Answer 1

79×3.9+3.9
=（79+1）x3.9
=80x（4-0.1）
=80x4-80x0.1
=320-8
=312

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Answer 2

79×3.9+3.9
=（79+1）x3.9
=80x3.9
=312

Answer 3

79×3.9+3.9
=（79+1）x3.9
=80x（4-0.1）
=80x4-80x0.1
=320-8
=312
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Answer 4

79×3.9+3.9
=3.9X(79+1)
=3.9X80
=(4-0.1)X80
=4X80-0.1X80
=320-8
=310+10-8
=310+2
=312

Answer 5

(1+79)×3.9＝80×3.9＝312