Walking 7/6 of his usual rate, a boy reaches his school 4 min early. Find his usual time to reach the school? Choose one:
A) 22 B) 28 C) 99 D) 77 E) 66
Speed Ratio = 1:7/6 = 6:7   Time Ratio = 7:6   1 -------- 7   4 --------- ? è 28 m   Answer:77
<result>D</result>
Walking 7/6 of his usual rate, a boy reaches his school 4 min early. Find his usual time to reach the school?