Question

A boat can travel 16 Kilometers per hour in still water. The boat travels 15 kilometers down a river and then 15 kilometers up stream. The entire trip takes 5.5 hours. Which equation describes the current, c, of the river?

a)

`(16)/(15 + c) + (16)/(15 - c) = 5.5`
b)

`(5.5)/(16 + c) + (5.5)/(16 - c) = 15`
c)

`(5.5)/(15 + c) + (5.5)/(15 - c) = 16`
d)

`(15)/(16 + c) + (15)/(16 - c) = 5.5`
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Answer 1

d)

Explanation:

the sites of the boat alone is 16 km/h.

downstream and upstream the effective speed is then influenced plus and minus by the current.

the distance traveled is 15km.

as speed = distance/time

then distance / speed = distance / (distance/time) = time

and we know the time it takes : 5.5 hours.

so, only answer d uses the right values in the "right places".