जॉइन Examsbookउत्तर : 3. "12 kmph"
If a girl cycles at 10 kmph, then she arrives at a certain place at 1 p.m. If she cycles at 15 kmph, she will arrive at the same place at 11 a.m. At what speed must she cycle to get there at noon?5
प्र: If a girl cycles at 10 kmph, then she arrives at a certain place at 1 p.m. If she cycles at 15 kmph, she will arrive at the same place at 11 a.m. At what speed must she cycle to get there at noon?
- 114 kmphfalse
- 213 kmphfalse
- 312 kmphtrue
- 411 kmphfalse
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उत्तर : 3. "12 kmph"
व्याख्या :
Answer: C) 12 kmph Explanation: The distance is constant in this case. Let the time taken for travel with a speed of 10 kmph be 't'. Now the speed of 15 kmph is 3/2 times the speed of 10 kmph. Therefore, time taken with the speed of 15 kmph will be 2t/3 (speed is inversely proportional to time) Extra time taken = t - 2t/3 = t/3 => 1pm - 11am = 2hrs => t/3 = 2h => t = 6 hrs. Now, Distance = speed x time = 10 x 6 = 60 kms Time he takes to reach at noon = 6 - 1 = 5 hrs Now, Speed = 60/5 = 12 kmph.