word problem
posted by Jessica .
2. The excursion boat Holiday travels 35km upstream and then back again in 4h 48min. If the speed of the Holiday in still water is 15km/h, what is the speed of the current?

speed of current  x km/h
speed against current  15x
speed with current  15+x
time against current = 35/(15x)
time with current = 35/(15+x)
so solve
35/(15x) + 35/(15+x) = 4.8
(I suggest multiplying each term by (5+x)(15x), you will end up with a quadratic equation )