Question

20．

估算． 3.92×5.1	7.2×0.8	30.125×2.98	45.02×19
2.49×0.38	4.9×3.8	0.58×68.75	42×58．

Answer 1

分析 根据小数乘法的估算方法：把相乘的因数看成最接近它的整数来算；据此解答即可．

解答 解：3.92×5.1≈4×5=20
7.2×0.8≈7×1=7
30.125×2.98≈30×3=90
45.02×19≈45×20=900
2.49×0.38≈2×0.5=1
4.9×3.8≈5×4=20
0.58×68.75≈0.6×70=42
42×58≈40×60=2400

点评 此题考查了小数乘法的估算方法，注意把相乘的数看成最接近它的整数．