SOLUTION: 10. I am racing my sister, but I get a two minute head start. If I run 7 mph and she runs 9 mph, how long will it take for her to catch up to me?

Question 688072: 10. I am racing my sister, but I get a two minute head start. If I run 7 mph and she runs 9 mph, how long will it take for her to catch up to me?
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
I am racing my sister, but I get a two minute head start. If I run 7 mph and she runs 9 mph, how long will it take for her to catch up to me?
.
change 2 minutes to hours:
2 * 1/60 = 2/60 = 1/30 hours (head start)
.
Let t = time (in hours) when she catches up
.
applying distance formula:
7(t+1/30) = 9t
multiplying both sides by 30:
7(30t+1) = 270t
210t+7 = 270t
7 = 60t
7/60 hours = t
or
7 minutes = t

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