A schoolboy covers his walk to school at 4 km/h and arrives 9 minutes late. The next day, he steps up his pace to 6 km/h and arrives 1 minute early. Find the distance. MCQ with Answer and Explanation
A schoolboy covers his walk to school at 4 km/h and arrives 9 minutes late. The next day, he steps up his pace to 6 km/h and arrives 1 minute early. Find the distance.
A. 2.2 km
B. 2.5 km
C. 1.8 km
D. 2.0 km
Answer: Option D
Solution (By JKExamLibrary)
Time difference = 9 - (-1) = 10 minutes = 10/60 = 1/6 hours. Let distance be d. d/4 - d/6 = 1/6 => d/12 = 1/6 => d = 2 km.
Explanation:
Let stream speed be c. Upstream speed = 15 - c, Downstream speed = 15 + c. Given: 2 * (15 - c) = 15 + c => 30 - 2c = 15 + c => 3c = 15 => c = 5 km/h.
A sound wave travels at a speed of 330 m/s. If the echo of a sound is heard from a wall after 2 seconds, find the distance of the wall from the source.
Explanation:
Total distance traveled by the sound wave to the wall and back = Speed * Time = 330 * 2 = 660 meters. Distance to the wall = 660 / 2 = 330 meters.
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