问题
解答题
计算下面各题.
(1)289.8÷18=______(验算)(2)1.55÷3.9≈______(保留两位小数)
(3)0.4×12.5×(4.2-1.7)=______(4)21.5÷[(6.07+2.53)×0.5]=______.
答案
(1)289.8÷18=16.1
16.1
18289.8
18 109
108 1 8
,18 0
验算:
16.1
× 1 8 128 8
;161 289.8
(2)1.55÷3.9≈0.40
0.397
3.91.55
1 17 380
351 290
;273 17
(3)0.4×12.5×(4.2-1.7),
=0.4×12.5×2.5,
=(0.4×2.5)×12.5,
=1×12.5,
=12.5;
(4)21.5÷[(6.07+2.53)×0.5],
=21.5÷[8.6×0.5],
=21.5÷4.3,
=5.
故答案为:16.1,0.40,12.5,5.