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)
$\frac{16}{15 + c} + \frac{16}{15 - c} = 5.5$
b)
$\frac{5.5}{16 + c} + \frac{5.5}{16 - c} = 15$
c)
$\frac{5.5}{15 + c} + \frac{5.5}{15 - c} = 16$
d)
$\frac{15}{16 + c} + \frac{15}{16 - c} = 5.5$
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Answer 1

Answer:

d)

Step-by-step 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".