A contractor estimated that one of her two bricklayers would take 9 hours to build a certain wall and the other 10 hours. However, she knew from experience that when they worked together, 10 fewer bricks were laid per hour. Since she was in a hurry, she put both workers on the job and found it took exactly 5 hours to build the wall. How many bricks did the wall contain?
X = number of bricks in the wall speed1 = X/9 bricks per hour speed2 = X/10 bricks per hour overhead = 10 bricks per hour speed3 = speed1 + speed2 - overhead = (X/9 + X/10 - 10) bricks per hour speed3 = X/5 bricks per hour X/9 + X/10 - 10 = X/5 X/9 + X/10 - X/5 = 10 10X + 9X - 18X = 900 X = 900 - jaan
I don't know Danny Boy I am definately not that bright; although I have never actually taken one of these tests before...