Jack rides in a motorboat against a river current for 36 km, the speed of the river current is 11.5 km/h while the speed of the motorboat in still water is 15 km/h.
What is an equation?
An equation is an expression that shows the relationship between two or more numbers and variables.
Let t represent the time on raft and a represent the speed of the current.
For motorboat:
(15 - a)(t + 9) = 36
t = [36 - 9(15 - a)]/(15 - a)
For raft:
(a + 15)t = 36
t = 36 / (a + 15)
Hence:
36 / (a + 15) = [36 - 9(15 - a)]/(15 - a)
a = 11.5 km/h
The speed of the river current is 11.5 km/h
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