Paper 1 · Mathematical Reasoning and Aptitude
UGC NET December 2023 (08.12.2023) Shift-II
The time taken by a motor boat moving downstream in a river to cover a distance and the time taken by the motor boat to cover the same distance upstream are in the ratio 3:5. If the speed of the stream is 10 km/hr, what is the speed of the boat?
A20 km/hr
B25 km/hr
C30 km/hr
D40 km/hr ✓ Correct
Correct answer: (D) 40 km/hr — The speed of the boat is 40 km/hr, so that is the answer.
Explanation
★The speed of the boat is 40 km/hr, so that is the answer.
★For the same distance, time is inversely proportional to speed.
★So the downstream speed to upstream speed ratio is 5 to 3.
★Downstream speed is boat speed plus 10 and upstream speed is boat speed minus 10.
★Setting boat plus 10 over boat minus 10 equal to 5 over 3 gives boat speed 40.
★So the speed of the boat is 40 km/hr.
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