Question
A car travels at 60 km/h to reach
its destination on time. If it travels at 65 km/h, it will reach the destination 30 minutes earlier. Find the time taken by the car to travel twice the distance at 70 km/h.Solution
ATQ, Let the usual time taken by the car be 'T' hours. Using, distance = speed × time We have, 'D' = 60T ----------- (I) And, 'D' = 65 × {T - (30/60)} -------- (II) From equation (I) and (II), We have, 60T = 65 × {T - (30/60)} Or, 60T = 65T - 65 × (30/60) Or, 5T = 32.5 Or, 'T' = 6.5 On putting the value of 'T' = 6.5 in equation (I), We have 'D' = 60 × 6.5 = 390 km So, the required time = (2 × 390) ÷ 70 = (780/70) = 11.14 hours
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