walking at 5 / 6 of its usual speed , a train is 10 minutes too late . find its usual time to cover the journey .
"new speed = 5 / 6 of the usual speed new time taken = 6 / 5 of the usual time taken so , ( 6 / 5 of the usual time ) - ( usual time ) = 10 min 1 / 5 of the usual time = 10 min usual time = 10 * 5 = 50 min correct option is a"
divide(10, subtract(inverse(divide(5, 6)), const_1))