Question

用简便方法计算下面各题。①2.5x2.8X4②4.8X3.6一3.8X3.6③(8十0.8)×1.

用简便方法计算下面各题。①2.5x2.8X4②4.8X3.6一3.8X3.6③(8十0.8)×1.25④7.09X99+7.09这怎么做

Answer 1

①2.5x2.8X4 乘法交换律+乘法结合律
=2.5x4x2.8
=10x2.8
=28
②4.8X3.6一3.8X3.6 乘法分配律
=3.6x(4.8-3.8)
=3.6x1
=3.6
③(8十0.8)×1.25 乘法分配律

=8x1.25+0.8x1.25
=10+0.1
=10.1
④7.09X99+7.09 乘法分配律
=7.09x(99+1)
=7.09x100
=709

Answer 2

1,,,,2.5*4*2.8=28

追答

2,,,（4.8-3.8）*3.6=3.6

3,,,8*1.25+0.8*1.25=11

4,,,7.09*（99+1）=709

求采纳

Answer 3

①2.5x2.8X4
=2.5×4×2.8
=10×2.8
=28
②4.8X3.6一3.8X3.6
=3.6×（4.8-3.8）
=3.6×1
=3.6
③(8十0.8)×1.25
=8×1.25+0.8×1.25
=10+1
=11
④7.09X99+7.09
=7.09×（99+1）
=7.09×100
=709