I had this problem on a test. I failed it there due to lack of time, but I still want to know if I can solve it. Did I do it right?
Code:
Pump 1 pumps up the oil in a tank in 24 H. Pump 2 pumps up the oil in 36 H. How many H does it take to pump up the oil if both of the pumps are working?
/----\
Work
/-------------\
/Capacity|H \
/-----------------\
After 100 units of work, the oil has been pumped up.
Work/Pump1 H = Pymp 1 Capacity
100/24 = 4,167
Work/Pump2 H = Pump 2 Capacity
100/36 = 2,778
Pump 1 Capacity+Pump 2 Capacity
4,167+2,778 = 6,945
Work/Capacity = H
100/6,945 ~= 14,4
4*0,6=2,4
Result: 14 H and 24 min