Brain Teasers
Building a house
Joe and Bob can build a house together in 45 days. Bob works exactly half the speed that Joe does. How many days can Joe and Bob each build a house on their own?
Answer
Since it takes them 45 days together to build one house, they can build 1/45 of a house in one day. Therefore you can set up an equation to add up each person's contribution to this 1/45 of a house:1/x + 1/2x = 1/45
Since the fractions on the left side of the equation represent each person's contribution, solving for x and then inverting each fraction will give their output in days/house:
Joe takes 67.5 days and Bob takes 135 days.
Hide Answer Show Answer
What Next?
View a Similar Brain Teaser...
If you become a registered user you can vote on this brain teaser, keep track of which ones you have seen, and even make your own.
Solve a Puzzle
Comments hidden to avoid spoilers.
Follow Braingle!