SOLUTION: Kelly drove north for 12 miles and then east for 9 miles at an average rate of 42 miles per hour to arrive at the town of Prime. Brenda left from the same location, at the same tim

Question 412454: Kelly drove north for 12 miles and then east for 9 miles at an average rate of 42 miles per hour to arrive at the town of Prime. Brenda left from the same location, at the same time, and drove along a straight road to Prime at an average 45 miles per hour. How many minutes earlier than Kelly did Brenda arrive?
I first tried drawing a diagram,then I tried using the formula d=rt, and I am not able to produce an anwer that makes sense. Please help me!
Answer by ewatrrr(24785) (Show Source): You can put this solution on YOUR website!



Hi

Kelly drove north for 12 miles and then east for 9 miles

Applying the Pythagorean Theorem to find the distance for the 'straight road'

 sqrt(144 + 81) = sqrt(225) = 15mi, length of straight road

 D = r*t OR t = D/r

     |Took Kelly 30 min

  |Took Brenda 20 min

How many minutes earlier than Kelly did Brenda arrive? 10min 

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