Question

Solve the original amount, before the changes
(a) 10% increase ended up being $100

(b) 10% decrease ended up being $90

(c) 10% decrease ended up being $100

Answer 1

(a) 110% = $100.  therefore 100% = ($100/110)x100 = $90.909090...

(b)90%=$90.  therefore 100% = ($90/90)x100=$100

(c) 90%=$100.  therefore 100% = ($100/90)x100=$111.11111...