walking 4 / 3 of his usual rate , a boy reaches his school 4 min early . find his usual time to reach the school ?
"speed ratio = 1 : 4 / 3 = 3 : 4 time ratio = 4 : 3 1 - - - - - - - - 4 4 - - - - - - - - - ? 16 m . answer : b"
multiply(4, 4)