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13 Jul 2016, 02:00
Kudos
Bookmarks
B
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Difficulty:
5%
(low)
Question Stats:
88% (01:20) correct
12%
(01:58)
wrong
based on 164
sessions
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Liz drove from point A to point B at 40 Km/h. On her way back she drove at 50 Km/h and therefore her way back lasted one hour less. What is the distance (in Km) between A and B?
A. 150.
B. 200.
C. 450.
D. 500.
E. 600.
A. 150.
B. 200.
C. 450.
D. 500.
E. 600.
13 Jul 2016, 02:38
Kudos
Bookmarks
Bunuel
Let time by t
Therefore, 40t = 50(t-1) ( since distance = speed*time)
We get t =5
So, distance is 200 km
Another way to look at this is, she increase her speed 25% and required 1 hours less. Since distance is constant, speed and time are inversely proportional. So 1 hour reduction equates to 20 % reduction in time. 20% is 1hour so 100% is 5 hour.
20% comes by this logic - If speed increased 1/x times then time reduces by 1/(x+1) and here x = 4.
13 Jul 2016, 05:13
Kudos
Bookmarks
Bunuel
Distance is same
S1t1=s2t2
40t= 50 (t-1)
t=5
distance= speed *time
40*5= 200
B is the answer
