百分數 ,,, 請 大 家 幫 忙 !!!

let 甲 = a, 乙 = b , ( for simplicity ), a,b are real numbers

=========== first question======================

by the given info., a = 1.2 b
=> b = 0.8333a ( cor. to 4d.p.)

i.e. b = 83.3333% a
(乙是甲的百分之 83.3333%)

============second question============================

a(1.25) = b
=> b = 0.8 a

therefore, the original value of a is 80% of b
(甲數原來的值是乙數的百分之80)

1.100/120x100%
120=甲(100%加20%)
100=甲減20%=乙
2.100/125x100%
125=乙
100=乙減25%=甲