脱式计算.6.8×0.75÷0.513.75÷0.125﹣2.7542÷(5.25÷0.25)1.53+23.4÷7.2.
估一估下面各式的结果大约是多少. 304×29≈ 560÷78≈ .
估算:92×47≈ ,539÷60≈ .
估一估. 409+394≈ 72×5≈ .