a train is walking at 6 / 7 of its usual speed , the train is 20 minutes too late . find its usual time to cover the journey .
new speed = 6 / 7 of the usual speed new time taken = 7 / 6 of the usual time taken so , ( 7 / 6 of the usual time ) - ( usual time ) = 20 min 1 / 6 of the usual time = 20 min usual time = 20 * 6 = 120 min = 2 hours correct option is e
divide(divide(multiply(divide(6, 7), 20), subtract(const_1, divide(6, 7))), const_60)