A man travelling at a speed of 20 km/ hr reached his office 10 minutes late. Next day he travelled at a speed of 30 km/ hr and he reached hisboffice 10 minutes earlier .The distance between his office and home is?
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Answer:
20 km
Step-by-step explanation:
Let d be the distance (in km) and let t be the time (in hr) that he has to get there.
Speed × time = distance
When speed is 20 km / hr, time is 10 minutes too long, and this is 1/6 hr, so the time (in hours) taken was t + (1/6). So
20 × ( t + 1/6 ) = d. (*)
When speed is 30 km / hr, he covers distance d in t - (1/6) hours. So
30 × ( t - 1/6 ) = d.
Together,
20 × ( t + 1/6 ) = 30 × ( t - 1/6 )
=> 2t + 2/6 = 3t - 3/6
=> t = 5/6.
Going back to (*) do get d, we find
d = 20 × ( t + 1/6 ) = 20 × ( 5/6 + 1/6 ) = 20 × 1 = 20.
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