alleryA boat goes 12 km upstream and 12 km back in 5 h. Current 1 km/h. Still-water speed?
A6 km/h
B5 km/h
C7 km/h
D4 km/h
Answer & Solution
Correct answer: B. 5 km/h
Upstream and downstream times give 12/(v−1)+12/(v+1)=5, whose valid root is v=5.
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