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Speed Time and Distance
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A is twice fast as B and B is thrice fast as C. The journey covered by C in 78 minutes will be covered by A in :

Answer & Solution
Correct Answer: Option A
The ratio of speeds of A, B, C = 6 : 3 : 1
The ratio of time taken by A, B, C = $$\frac{1}{6}$$ : $$\frac{1}{3}$$ : 1
To simplify it, we will multiply it by LCM of ratio of speeds given.
Hence, the ratio of time taken by A, B, C = 1 : 2 : 6
[Speed is inversely proportional to time, means if speed increase time decreases. So, ratio of time would be reciprocal of the ratio of speed given. ]
Time taken by C to covered given distance = 78 = 6 × 13
The ratio of time of A and C = 1 : 6
Thus, time taken by A = 13 min.
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2 Comments
MD Rakib
MD Rakib 8 years ago
SPEED RATIO=A:B:C=6:3:1
TIME RATIO =1:2:6[LCM OF[ 6,3 &1=6]
SO 6 FOR 78
1 FOR 78/6=13...(ANS)
Phani
Phani 11 years ago
i want clear explanation