Car A and car B travel around a circular park with a radius of 20 miles. Both cars leaves from the same point. Car A travels counter-clockwise at 60 miles per hour and car B travels clockwise at 40 miles per hour. Car B leaves 20 minutes after car A. Approximately how many minutes does it tak for the cars to meet after car A starts?
A. 63
B. 75
C. 83
D. 126
E. 188
My problem is that answers coming differently if I adopt different methods. What am I doing wrong ?
Solution A:
Total distance to be covered by both cars approx = 2 x 3.14 x 20 = 125.6 miles
Since car A has already left 20 mint ago - it has already travelled = 20 miles
The distance now remained to be covered by both cars is approx = 106 miles
Car B now starts after 20 mints
(Relative Rates) x T = total dist to be covered
100T = 100.6
T=1.06 .. approx 63 mints
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Solution B:
Distance by Car A + Distance by Car B = Total Distance
60T + 40(T-20/60) = 125.6
100T - 40/3 = 125.6
T = 1.39
approx = 83 minutes
Correct answer is 83 and not 63 mintes - whats the difference b/w two solutions. I got this wrong since I used Solution A.
A. 63
B. 75
C. 83
D. 126
E. 188
My problem is that answers coming differently if I adopt different methods. What am I doing wrong ?
Solution A:
Total distance to be covered by both cars approx = 2 x 3.14 x 20 = 125.6 miles
Since car A has already left 20 mint ago - it has already travelled = 20 miles
The distance now remained to be covered by both cars is approx = 106 miles
Car B now starts after 20 mints
(Relative Rates) x T = total dist to be covered
100T = 100.6
T=1.06 .. approx 63 mints
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Solution B:
Distance by Car A + Distance by Car B = Total Distance
60T + 40(T-20/60) = 125.6
100T - 40/3 = 125.6
T = 1.39
approx = 83 minutes
Correct answer is 83 and not 63 mintes - whats the difference b/w two solutions. I got this wrong since I used Solution A.
