用简便方法计算．2.4+2.4×9 20.6×101-20.6 9.8×3.6 7.5×1.9×0.4．
第1个回答 2014-08-13
①2.4+2.4×9
=2.4×（9+1）
=2.4×10
=24；
②20.6×101-20.6
=20.6×（101-1）
=20.6×100
=2060；
③9.8×3.6
=（10-0.2）×3.6
=10×3.6-0.2×3.6
=36-0.72
=35.28；
④7.5×1.9×0.4
=（7.5×0.4）×1.9
=3×1.9
=5.7．
=2.4×（9+1）
=2.4×10
=24；
②20.6×101-20.6
=20.6×（101-1）
=20.6×100
=2060；
③9.8×3.6
=（10-0.2）×3.6
=10×3.6-0.2×3.6
=36-0.72
=35.28；
④7.5×1.9×0.4
=（7.5×0.4）×1.9
=3×1.9
=5.7．
