Ravi leave for his school from his house on his cycle at 8:20 a.m. If he run his cycle at a speed of 10 km/h, he reaches his school 8 minutes late, and if he drives the cycle at a speed of 16 km/h, he reaches his school 10 minutes early. Find the time at which school starts.
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e 9:00 a.m.
| Understanding | Application |
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Ravi travel from his house to his school in both the cases means Ravi travel same distance but the speed of Ravi is different in both cases and time is also different let the distance between Ravi's house and school is y km and time taken to reach the school at a time is t hours. As we know, Speed = Distance/Time So, Distance = Speed/Time |
Distance when ravi travel with 10 km/h y = 10(t + 8/60) Distance when ravi travel with 16 km/h y = 16(t - 10/60) Now , 10(t + 8/60) = 16(t - 10/60) 5(t + 8/60) = 8(t - 10/60) 5t + 40/60 = 8t - 80/60 3t = (2/3) + (4/3) 3t = (2 + 4)/3 3t = 2 t = 2/3 hours or (2/3) × 60 = 40 mins As given Ravi start at 8:20 a.m so now time is 8:20 + 40 mins = 9 a.m |