用简便方法计算.0.3×2.5×0.4 0.78×101 2.5×(8+0.4) 1.25×0.7×0.8 9.8×2.5 50.8×101-

2024-12-03 06:34:38
推荐回答(1个)
回答1:

①0.3×2.5×0.4
=0.3×(2.5×0.4)
=0.3×1
=0.3;

②0.78×101
=0.78×(100+1)
=0.78×100+0.78
=78+0.78
=78.78;

③2.5×(8+0.4)
=2.5×8+2.5×0.4
=20+1
=21;

④1.25×0.7×0.8
=(1.25×0.8)×0.7
=1×0.7
=0.7;

⑤9.8×2.5
=(10-0.2)×2.5
=10×2.5-0.2×2.5
=25-0.5
=24.5;

⑥50.8×101-50.8
=50.8×(101-1)
=50.8×100
=5080;

⑦4.6×99+4.6
=4.6×(99+1)
=4.6×100
=460;

⑧0.25×32×0.125
=0.25×4×8×0.125
=(0.25×4)×(8×0.125)
=1×1
=1;

⑨38.2×8+61.8×8
=(38.2+61.8)×8
=100×8
=800.