Walking 6/7 of his usual rate, a boy reaches his school 4 min early. Find his usual time to reach the school? Answers:
A) 28 m	B) 20 m	C) 22 m	D) 23 m	E) 24 m

Rationale: speed ratio = 1 : 6 / 7 = 7 : 6 time ratio = 6 : 4 1 - - - - - - - - 6 4 - - - - - - - - - ? = > 24 m answer : e
Answer: E