walking 6 / 7 of his usual rate , a boy reaches his school 4 min early . find his usual time to reach the school ?
speed ratio = 1 : 6 / 7 = 7 : 6 time ratio = 6 : 4 1 - - - - - - - - 6 4 - - - - - - - - - ? = > 24 m answer : e
multiply(4, 6)