Problem:
Carlos took of a whole pie. Maria took one third of the remainder. What portion of the whole pie was left?
Answer Choices:
A.
B.
C.
D.
E.
Solution:
If Carlos took of the pie, there must be left. After Maria takes of the remaining of the remaining is left.
Therefore, the answer is .
OR
Like solution , it is clear that there is of the pie remaining. Since Maria takes of the remainder, she takes , meaning that there is left.
OR
We have
(100 \%-70 \%) \cdot\left(1-\dfrac{1}{3}\right)=30 \% \cdot \dfrac{2}{3}=\boxed
of the whole pie left.
The problems on this page are the property of the MAA's American Mathematics Competitions