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Question
A car travels a distance of x km at a speed of `5 5/9` m/sec and returns at 5m/sec to the starting point. If the total time taken by the car in `7 3/5` hours then the value of x (in km) is:
Options
72
66
78
80
MCQ
Solution
72
Explanation:
Speed of going = `5 5/9` m/s = `50/9` m/s
= `50/9 xx 18/5` = 20 km/hr
Speed of returning = 5 m/s = `5 xx 18/5` = 18 km/hr
Total time during entire journey = `x/20 + x/18`
A.T.Q,
= `x/20 + x/18 = 7 3/5`
⇒ `(9x + 10x)/180 = 38/5`
∴ `x = 2/5 xx 180` = 72 km
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Time, Speed and Distance (Entrance Exam)
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