Question : A boat can cover 120 km upstream and back in a total of 30 hours, and 25 km upstream and 40 km downstream in a total of 7 hours. How much distance will the boat cover in 16 hours in still water?
Option 1: 200 km
Option 2: 180 km
Option 3: 175 km
Option 4: 225 km
Correct Answer: 200 km
Solution :
Let the speed of the boat in still water be
Speed downstream =
Speed upstream =
Now,
and
Multiplying equation (2) by 3, we get,
Subtracting equation (3) from (1), we get,
Putting the value of
Solving these two equations, we get the values of
Distance covered by the boat in 16 hours in still water = 16 × 12.5 = 200 km
Hence, the correct answer is 200 km.
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