Problem: If the price of an article is increased by per cent p, then the decrease in per cent of sales must not exceed d in order to yield the same income. The value of d is:
Answer Choices:
A. 1/(1+p)
B. 1/(1−p)
C. p/(1+p)
D. p/(p−1)
E. (1−p)/(1+p)
Solution:
Let s be the price of the article, n the number of sales. Then [(1+p)s][(1−d)n]=sn,p−d−pd=0,d=p/(1+p).