Math in the Real World: Counting Problems
The practical applications of math in the real world, from intrepid U.S. Post Office employee James Wu.
“This is a wall panel for an apartment building in Boston. It has five floors, and each floor has the same number of apartments. I have a package for #49–the buzzer doesn’t work very well, but they tell me to go up. What floor do I go to?”
Work out a solution before clicking “More”.
Solution: The image shows apartments from 35 to 59. How many apartments is that? To count members of a consecutive set, subtract and then add one: 59 – 35 + 1 = 25 apartments.
Since there are five floors and an equal number of floors per apartment, that’s five apartments per floor.
Thus, the first floor contains 35, 36, 37, 38, and 39.
The second floor contains 40, 41, 42, 43 and 44.
The third floor contains 45, 46, 47, 48, and 49.
The answer is “the third floor.”
See the Manhattan GRE Word Problems Strategy Guide for more (and more challenging) counting problems.
Also see this waggish video about more complicated counting situations:
//www.youtube.com/watch?v=M7PlJM2aCho