解:78.5乘以( 0.6 )等于47.1
∵已知78.5×一个数 = 47.1
需求出这个数为多少
∴设这个数为x
78.5 × x = 47.1
x = 47.1 ÷ 78.5
x = (47×10+1)/10 ÷ (78×10+5)/10
x = 471/10 ÷ 785/10
x = 471/10 × 10/785
x = 471/785
x = 3/5
∴x = 0.6
答:78.5乘以0.6等于47.1
解:47.1÷78.5=0.6
答:78.5×0.6=47.1