In the new budget the price of milk rose by 20%. By how much percent must a person reduce his consumption so that his expenditure on it does not increase?  Choose one.
A) 7.5 %	B) 9.1 %	C) 10.9 %	D) 16.67 %	E) 15 %

Rationale: reduce in consumption = r / ( 100 + r ) * 100 % = 20 / 120 * 100 = 16.67 % answer is d
Answer: D