SOLUTION: David is 1/4 mile from home bicycling at 21 mph when his brother takes off on his bike from home trying to catch him. How fast must David�s brother go to catch David a mile from h

Question 692583: David is 1/4 mile from home bicycling at 21 mph when his brother takes off on his bike from home trying to catch him. How fast must David�s brother go to catch David a mile from home?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
David is 1/4 mile from home bicycling at 21 mph, when his brother takes off on his bike from home trying to catch him.
How fast must David�s brother go to catch David a mile from home?
:
Brother has to ride 1 mile while David rides 3/4 of a mile (use .75 mi)
:
Let s = brothers required speed, to accomplish this
:
Write a time equation, time = dist/speed
:
=
cross multiply
.75s = 1 * 21
s =
s = 28 mph
;
:
Find the times, should be equal
1/28 = .0357 hrs
.75/21 = .0357
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