Walking 7/6 of his usual rate, a boy reaches his school 7 min early. Find his usual time to reach the school?  Select the correct option:
A) 22
B) 28
C) 99
D) 49
E) 66

Rationale: "speed ratio = 1 : 7 / 6 = 6 : 7 time ratio = 7 : 6 1 - - - - - - - - 7 7 - - - - - - - - - ? 49 m answer : d"
Answer: D