Subject
Quantitative Aptitude
Topic
Speed & Distance
A man can row upstream at 8 kmph and downstream at 13 kmph. The speed of the stream is :
A man can row upstream at 8 kmph and downstream at 13 kmph. The speed of the stream is :
ক)
2.5km/ hrখ)
4.2 km/ hrগ)
5 km/ hrঘ)
10.5 km / hrExplanation
Given: Upstream speed = 8 kmph Downstream speed = 13 kmph Find: Speed of the stream Method 1: Detailed Solution Let: Speed of boat in still water = B kmph Speed of stream = C kmph Setting up equations: Downstream: Boat speed + Stream speed = B + C = 13 kmph ... (1) Upstream: Boat speed - Stream speed = B - C = 8 kmph ... (2) Solving the system of equations: Adding equations (1) and (2): (B + C) + (B - C) = 13 + 8 2B = 21 B = 10.5 kmph Subtracting equation (2) from (1): (B + C) - (B - C) = 13 - 8 2C = 5 C = 2.5 kmph Verification: Downstream: 10.5 + 2.5 = 13 kmph ✓ Upstream: 10.5 - 2.5 = 8 kmph ✓ ---------------------------------------------------------------- Method 2: Shortcut Formula Direct formula for stream speed: Speed of stream = ½(Downstream speed - Upstream speed) = ½(13 - 8) = ½ × 5 = 2.5 kmph Bonus formula for boat speed: Speed in still water = ½(Downstream speed + Upstream speed) = ½(13 + 8) = ½ × 21 = 10.5 kmph Therefore, the answer is A) 2.5 km/hr .Related questions
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