Question

a分之（b+1）=0.25 （a-1）分之b=0.2 a和b各是多少,

Answer 1

（b+1）/a=0.25 ====>b+1=0.25a--------1)

b/（a-1）=0.2======>b=0.2(a-1)--------2)

1)-2)得

1=0.05a+0.2

a=16

b=3

找规律 1 3 5 20

3 5 7 56

5 a b c

则C=(5+a)b=(5+7)×9=108