Algebrahard · Past Paper
A boat goes 30 km upstream and 44 km downstream in 10 hours. In 13 hours, it can go 40 km upstream and 55 km downstream. Find the speed of the boat in still water.
A8 km/h
B5 km/h
C11 km/h
D3 km/h
✓ Correct Answer: A — 8 km/h
Let upstream speed be u and downstream speed be d. 30/u + 44/d = 10, 40/u + 55/d = 13. Solving gives u=5, d=11. Speed in still water = (d+u)/2 = 8 km/h.
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