Question
If a car runs at 30 km/hr, it reaches its destination
late by 15 minutes but if runs at 45 km/hr it is late by 7 minutes. What is the correct time for the journey?Solution
Distance = Difference in time x (S1 x S2)/(S1 – S2) D = [15 – 7]/60 x {(30 x 45)/[45 – 30]} => (8/60) x (30 x 45)/15 => 12 km Time, T = D/S (take any one of the speed) => 12/30 = 12/30 x 60 = 24 minutes Then, correct time is 24 – 15 = 9 minutes
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