Walking 7/6 of his usual rate, a boy reaches his school 4 min early. Find his usual time to reach the school? Pick one:  A) 21  B) 16  C) 16  D) 28  E) 12
Speed Ratio = 1:7/6 = 6:7   Time Ratio = 7:6   1 -------- 7   4 --------- ? è 28 m   Answer: 28
<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?