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carollaw
10-06-2008, 07:41 PM
I'l having aproblem with distance. I know that d=rt but I cant seem ot solve the following:

Carol and Marla drove a total of 258 miles in 5 hours. Carol drove the first part and averaged 53 mph. Marla drove the rest and averaged 51 mph. For approx how many hours did Marla drive?

Thanks for your help!

Subhotosh Khan
10-06-2008, 09:21 PM
I'l having aproblem with distance. I know that d=rt but I cant seem ot solve the following:

Carol and Marla drove a total of 258 miles in 5 hours. Carol drove the first part and averaged 53 mph. Marla drove the rest and averaged 51 mph. For approx how many hours did Marla drive?

Thanks for your help!

Name things first:

Miles(d) driven by Carol = C

Miles driven by Marla = M

Total miles driven = C + M = 258............................................... .......(1)

Time (d/r) driven by Carol = C/53

Time (d/r) driven by Marla = M/51

Total time driven = 5 = C/53 + M/51................................................ .(2)

You have two equations - two unknowns - solve it.

soroban
10-07-2008, 03:06 PM
Hello, carollaw!


Carol and Marla drove a total of 258 miles in 5 hours.
Carol drove the first part and averaged 53 mph.
Marla drove the rest and averaged 51 mph.
For how many hours did Marla drive?
\text{Let }x\text{ = hours that Marla drove.}

. . \text{At 51 mph, she drove: }\:51x\text{ miles.}


\text{Carol drove the other }5-x\text{ hours.}

. . \text{At 53 mph, she drove: }\:53(5-x)\text{ miles.}


\text{Together, they drove a total of: }\:51x + 53(5-x)\text{ miles.}


\text{But we are told they drove a total of 258 miles.}

. . There\text{ is our equation! }\quad\hdots\quad 51x + 53(5-x) \:=\:258


. . Got it?