two cranes can unloud a ship together in 12 hours. The faster crane takes 10 hours less than the slower crane, if each were to unload the same ship alone. How long does it take for each crane to unload this ship?
Rate of SLOWER crane = 1 ship / (x -10 )
Rate of FASTER crane = 1 ship / x
Now for one ship with both working the time = 12 hrs:
1 ship / ( 1/(x-10) + 1/x) = 12 hr <==== solve for 'x'
1 = 12/(x-10) + 12 / x
x^2 - 10x = 12x + 12x-120
x^2 -34x +120 = 0 Use Quadrtaic Formula ( or factoring) to find x = 30 or 4 (extraneous)
so one crane takes 30 hours the other takes 20 hours alone