Problem: Successive discounts of 10% and 20% are equivalent to a single discount of:
Answer Choices:
A. 30%
B. 15%
C. 72%
D. 28%
E. none of these
Solution:
Let P be the original price. Then a discount of 10% gives a new price P−.1P=.9P. Following this by a discount of 20%, we have
.9P−.2(.9P)=.72P
Thus the net discount is P−.72P=.28P or 28%;
or
net discount =d1+d2−d1d2=10010+10020−1002=28%