Problem:
The price of an article is cut 10%. To restore it to its former value, the new price must be increased by:
Answer Choices:
A. 10%
B. 9%
C. 1191%
D. 11%
E. none of these answers
Solution:
Let M be the original marked price. After a 10% discount, the new price is M−0.1M=0.9M.
To restore the price from 0.9M back to the original price, M, we need to add back the discounted amount, which is 0.1M.
The required percentage increase must be calculated based on the new, lower price (0.9M), not the original price.
Percentage Increase=New PriceAmount to Add×100%=0.9M0.1M×100%=91×100%=11.1%=1191%
Therefore, an increase of 1191% is required to restore the original price.