Fraction problem

Question

A bag of flour weighed 2.8 kg. Amy used some flour to bake cupcakes and cookies. The amount of flour used to bake cookies was 4 times the amount of flour used to bake cupcakes. She was left with 0.765 kg of flour. How much flour did Amy use to bake cupcakes?

Answer 1

2.800 - 0.765 = 2.035 kg used

 

Here's where it gets tricky again. The amount of floor for cookies was 4 times the amount for cupcakes, so you might think you would take 1/4 of 2.035.

 

However, if we do 4 parts cookies for one part cupcakes, we have FIVE total parts. 1/5 is used for cupcakes and 4/5 is used for cookies!

 

(1/5)(2.035) = 0.407 kg

 

Let's make sure...

 

0.407 + 4(0.407) = 5(0.407) = 2.035

 

Boom.