7.5*2.3+1.9*2.5+22.5*0.4===要用简便算法

Question

7.5*2.3+1.9*2.5+22.5*0.4
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要用简便算法

Answer 1

7.5*2.3+1.9*2.5+22.5*0.4
=2.5*(3*2.3) + 2.5*1.9 + 2.5*(9*0.4)
=2.5*(6.9 + 1.9 + 3.6)
=2.5*12.4
=(2.5*4) * 3.1
= 10 * 3.1
= 31