Problem: If the base of a rectangle is increased by 10% and the area is unchanged, then the altitude is decreased by:
Answer Choices:
A. 9%
B. 10%
C. 11%
D. 1191​%
E. 9111​%
Solution:
bh=(1011​b)(xh)∴x=1110​ and h is reduced by 111​ or 9111​%;
or
bh=(b+101​b)(h−100r​h)=bh+101​bh−100r​bh−1000r​bh
∴101​−100r​−1000r​=0 and r=9111​ (per cent).