题目内容
【题目】能用简便的尽量简便计算。
①0.4×7.5×2.5 ②4.2×7.8+2.2×4.2
③8.79×101 ④ 8.4÷0.20÷0.5
【答案】7.5 42 887.79 84
【解析】
① 0.4×7.5×2.5 ② 4.2×7.8+2.2×4.2
=0.4×2.5×7.5 =4.2×（7.8+2.2）
=1×7.5 =4.2×10
=7.5 =42
③ 8.79×101 ④ 8.4÷0.20÷0.5
=8.79×(100+1) =8.4÷（0.20×0.5）
=8.79×100+8.79×1 =8.4÷0.1
=879+8.79 =84
=887.79
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