设一共计划做A个题
(3/4)*A + A*(1 - 3/4)*20% + 30 = A*(1 + 30%)
0.75 *A + 0.05*A + 30 = 1.3*A
0.5*A = 30
A = 60
答:原计划做60个题
回答
30 ÷ [(1 + 30%) - 3/4 - (1 - 3/4)*20%]
= 30 ÷ (1.3 - 0.75 - 0.05)
= 30 ÷ 0.5
= 60
你可以套
设一共计划做A个题
(3/4)*A + A*(1 - 3/4)*20% + 30 = A*(1 + 30%)
0.75 *A + 0.05*A + 30 = 1.3*A
0.5*A = 30
A = 60
答:原计划做60个题
回答
30 ÷ [(1 + 30%) - 3/4 - (1 - 3/4)*20%]
= 30 ÷ (1.3 - 0.75 - 0.05)
= 30 ÷ 0.5
= 60
你可以套