Working together, merry and pippin can build a wall in 4.5 hours. if merry can do the job alone in 6 hours working alone, how long would it take pippin to build the wall when working alone?
Accepted Solution
A:
Merry builds 100% wall for 6 hours. For 4.5 hours she did 75% of wall (4.5 * 100 /6) , rest 25% did another girl for 4.5 hours. If she builds wall alone she would spend 18 hours.