Yesterday I bought 3/4 of a pizza. I ate 1/5 of it. How much pizza did I have left?

Question

How is 11/20 the answer?

 

Answer 1

The problem is poorly worded.

 

What does "it" mean?  If "it" means 3/4 of a pizza, then you ate (1/5)(3/4)=3/20, leaving 15/20 - 3/20 = 12/20 = 3/5.

 

If "it" means a whole pizza, then you ate 1/5 = 4/20, leaving 15/20 - 4/20, which is 11/20.

 

You are right to question this.