What is the percent change in unit price of a bag of cookies if the number of cookies per box is decreased by 15% (with no change in the price per bag) ?

A) 17.6%
B) 15%
C) 20%
D) 10%
E) 11.1%

The percent change in unit price can be calculated using the formula for percent increase, which is (New Value - Original Value) / Original Value * 100%. If the number of cookies decreases by 15%, the new quantity is 85% of the original. Since the price remains the same but you get 85% of the cookies, the price per cookie increases. To find the percent increase in unit price, you can think of it as the inverse of 85%, which is 1/0.85 = 1.176. This means the unit price increases by 17.6% to maintain the original price for fewer cookies.