Calculus Check
posted by Matt on .
A survey of one thousand people found that 70% of the people have a
CD player, 85% have a telephone, and 45.2% have a computer. At
least how many people have all three objects?
Is the answer 152?

The minimum number will start with the 15 percent who do not have a telephone:
So 150 of 452 have a computer, but no telephone.
The next group has to be having a telephone and a computer, but not cd player.
300 do not have a cd player, so you can take these 300 and make them owners of a computer.
That leaves 2 people who have to have all three.