Suppose that 25% of all the wise people are nice and half of all the nice
people are wise. Suppose further that 25% of all the people are neither
wise nor nice. What percent of all the people are both wise and nice?	Choose the correct choice from the following.
A) 10%
B) 15%
C) 20%
D) 25%
E) 30%
Let k be the number of all the people who are both nice and wise. Then, the   number of wise people is 4k and the number of nice people is 2k. The number of people   who are either wise or nice or both is 4k + 2k − k = 5k. If the number of all people is   x, then x − 0.25x = 5k, so x = 20k/3.   correct answer 15%
<result>B</result>
Suppose that 25% of all the wise people are nice and half of all the nice
people are wise. Suppose further that 25% of all the people are neither
wise nor nice. What percent of all the people are both wise and nice?