what is the length of time that Kathy drove?

Question

kathy and leslie drive a total of 669 miles in 12 hours. Kathy drove the first part of the trip and averaged 65 miles per hour. Leslie drove the remainder of the trip and averaged 35 miles per hour. For what length of time did Kathy drive.

Answer 1

669 miles in 12 hrs.

 

kathy's speed      65miles/hr

Leslie's speed      35miles/hr

 

total time driven is 12 hours

 

so,

 

65(t) + 35(12 - t) = 669

 

65t + 420 - 35t = 669

65t - 35t = 669 -420

 

30t = 249

 

t= 8.3 hours

 

Kathy drove for 8.3 hours