简便计算. 87.4×33+87.4×68-87.4 5.7×10.1 12.5×0.25×0.8×40 0.279×355+0.645×279.
问题描述:
简便计算. 87.4×33+87.4×68-87.4 |
5.7×10.1 |
12.5×0.25×0.8×40 | 0.279×355+0.645×279. |
答
(1)87.4×33+87.4×68-87.4,=87.4×(33+68-1),=87.4×100,=8740;(2)5.7×10.1,=5.7×(10+0.1),=5.7×10+5.7×0.1,=57+0.57,=57.57;(3)12.5×0.25×0.8×40,=(12.5×0.8)×(0.25×40),=10×...