(1) 某數的100%加80%後除以60%,得出該數的40%減20%,求那數。
解:設某數是x。
( 100% x + 80% ) ÷ 60% = 40% x - 20%
( x + 0.8 ) ÷ 3/5 = 0.4 x - 0.2
( x + 0.8 ) × 5/3 = 0.4 x - 0.2
5x + 4 = 1.2x - 0.6
3.8x = -4.6
x = -23/19
答:某數是-23/19。
(2) A是B的23.275%,那麼B是A的百分之幾?
解:
A = 23.275% B
A = 23.275B / 100
100A / 23.275 = B
B = (100/23.275) A
B = (4000/931) A
B = (400000/931)% A
答:B是A的(400000/931)%,即約429.6455424%。