Two boys starting from the same place walk at a rate of 5kmph and 5.5kmph respectively. What time will they take to be 10.5km apart, if they walk in the same direction?	Pick.
A) 15 hours
B) 16 hours
C) 17 hours
D) 18 hours
E) 21 hours
The relative speed of the boys = 5.5kmph â€“ 5kmph   = 0.5 kmph   Distance between them is 10.5 km   Time = Distance/Speed   Time= 10.5km / 0.5 kmph = 21 hrs   answer :21 hours
<result>E</result>
Two boys starting from the same place walk at a rate of 5kmph and 5.5kmph respectively. What time will they take to be 10.5km apart, if they walk in the same direction?