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07 May 2017, 13:45
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D
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:
73% (02:14) correct
27%
(02:37)
wrong
based on 325
sessions
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At 7 a.m. John leaves his home riding his bicycle due west, at a speed of 11 miles per hour, toward Mark's house, which is 260 miles away. Five hours later Mark leaves his home along the same route to John's house on his bicycle traveling at 9 miles per hour. At what time do they meet each other on the way?
A. 1:00 p.m.
B. 5:00 p.m.
C. 8:15 p.m.
D. 10:15 p.m.
E. 10:25 p.m.
A. 1:00 p.m.
B. 5:00 p.m.
C. 8:15 p.m.
D. 10:15 p.m.
E. 10:25 p.m.
Updated on: 20 May 2017, 01:48
Originally posted by guptarahul on 19 May 2017, 03:47.
Last edited by guptarahul on 20 May 2017, 01:48, edited 1 time in total.
Last edited by guptarahul on 20 May 2017, 01:48, edited 1 time in total.
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Before solving this question lets revise one concept
“Relative” means “in comparison to”. We use the concept of relative Speed when we have two or more bodies moving with some Speeds. To make things simpler, we make one body stationary (Speed =zero) and take the Speed of the other body with respect to the stationary body, which is the sum of the Speeds if the bodies are moving in the opposite direction and the difference if they are moving in the same direction. This Speed of the moving body with respect to the stationary body is called Relative Speed.
Relative Speed of 2 bodies = Sum of their individual Speeds if they are moving in the opposite direction = Difference of their individual Speeds if they are moving in the same direction
Now coming back to question.
Distance traveled by John in 5 hours = 5 * 11 = 55 miles.
using distance = speed * time
Time after 5 hours = 12 pm
Distance remaining to Mark's house = 260 - 55 = 205 miles
Time taken for Mark and John to meet = 205/(11+9) = 205/20 hours = 10.25 hours = 10 hours 15 mins.
RELATIVE SPEED
“Relative” means “in comparison to”. We use the concept of relative Speed when we have two or more bodies moving with some Speeds. To make things simpler, we make one body stationary (Speed =zero) and take the Speed of the other body with respect to the stationary body, which is the sum of the Speeds if the bodies are moving in the opposite direction and the difference if they are moving in the same direction. This Speed of the moving body with respect to the stationary body is called Relative Speed.
Relative Speed of 2 bodies = Sum of their individual Speeds if they are moving in the opposite direction = Difference of their individual Speeds if they are moving in the same direction
Now coming back to question.
Distance traveled by John in 5 hours = 5 * 11 = 55 miles.
using distance = speed * time
Time after 5 hours = 12 pm
Distance remaining to Mark's house = 260 - 55 = 205 miles
Time taken for Mark and John to meet = 205/(11+9) = 205/20 hours = 10.25 hours = 10 hours 15 mins.
General Discussion
07 May 2017, 14:33
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after 5 hours john already run 55miles, so he is 260-55=205 miles away from mark.
at the time Tj=Tm, VjTj + VmTm = 205 ---> Tj=Tm=205/(Vj+Vm)
= 205/20 --> 10,25 hours
we are at 12.00am + 10,25 hours = they will meet at 10:15pm so [D]
at the time Tj=Tm, VjTj + VmTm = 205 ---> Tj=Tm=205/(Vj+Vm)
= 205/20 --> 10,25 hours
we are at 12.00am + 10,25 hours = they will meet at 10:15pm so [D]
