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fitzpratik
Posts: 224
26 Dec 2018, 20:16
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C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
35%
(medium)
Question Stats:
75% (02:10) correct
25%
(02:22)
wrong
based on 191
sessions
History
Date
Time
Result
Not Attempted Yet
A cyclist climbs a hill with a length of 400 m with a speed of 7.2 km/h. When descending, the speed is two times greater. How much time is necessary for the cyclist to climb and descend the hill?
A. 100 Seconds
B. 200 Seconds
C. 300 Seconds
D. 400 Seconds
E. 500 Seconds
A. 100 Seconds
B. 200 Seconds
C. 300 Seconds
D. 400 Seconds
E. 500 Seconds
Updated on: 15 Jul 2020, 10:57
Originally posted by BrushMyQuant on 27 Dec 2018, 04:23.
Last edited by BrushMyQuant on 15 Jul 2020, 10:57, edited 1 time in total.
Last edited by BrushMyQuant on 15 Jul 2020, 10:57, edited 1 time in total.
Kudos
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If the Question is Speed (coming down) = Two Times of Speed (going up)
While going up the time taken is d/s (Distance/speed)
while coming down time taken is d/2s (Speed is 2 times => 2 times of the speed while going up)
Total time = d/s + d/(2s) = 3d/(2s)
d= 400m = 0.4km
s = 7.2 km/hr
time = 3d/(2s) = 3*0.4 / (2*7.2) hr = 12/(2*72) hr = 1*3600/12 sec = 300s
So, Answer is C
If the Question is Speed (coming down) = Two Times greater than Speed (going up)
While going up the time taken is d/s (Distance/speed)
while coming down time taken is d/3s (Speed is 2 times greater => 3 times of the speed while going up)
Total time = d/s + d/(3s) = 4d/(3s)
d= 400m = 0.4km
s = 7.2 km/hr
time = 4d/(3s) = 4*0.4 / (3*7.2) hr = 16/(3*72) hr = 16*3600/(3*72) sec = 16*50/3 sec = 800/3 sec = 267 sec
So, either the questions needs to be updated or 267 has to be added as an option choice!
Hope it helps!
While going up the time taken is d/s (Distance/speed)
while coming down time taken is d/2s (Speed is 2 times => 2 times of the speed while going up)
Total time = d/s + d/(2s) = 3d/(2s)
d= 400m = 0.4km
s = 7.2 km/hr
time = 3d/(2s) = 3*0.4 / (2*7.2) hr = 12/(2*72) hr = 1*3600/12 sec = 300s
So, Answer is C
If the Question is Speed (coming down) = Two Times greater than Speed (going up)
While going up the time taken is d/s (Distance/speed)
while coming down time taken is d/3s (Speed is 2 times greater => 3 times of the speed while going up)
Total time = d/s + d/(3s) = 4d/(3s)
d= 400m = 0.4km
s = 7.2 km/hr
time = 4d/(3s) = 4*0.4 / (3*7.2) hr = 16/(3*72) hr = 16*3600/(3*72) sec = 16*50/3 sec = 800/3 sec = 267 sec
So, either the questions needs to be updated or 267 has to be added as an option choice!
Hope it helps!
04 Jun 2019, 23:51
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fitzpratik
We can solve this by converting units to m/s:
7.2 km/h = 7.2 * 1000 * 1/60 * 1/60 = 2m/s
Provided the question means to say 'speed when descending is twice the speed of climb'
we have,
t= 400/2 + 400/4 = 300m/s
Option C
