SOLUTION: Elisa walked a certain distance at 5mi/h and then jogged twice that distance a 8 mi/h. Her total time walking and jogging was 2 hr and 15 min. How many miles did she walk? I am

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Question 219376: Elisa walked a certain distance at 5mi/h and then jogged twice that distance a 8 mi/h. Her total time walking and jogging was 2 hr and 15 min. How many miles did she walk?
I am trying to use the formula time= distance/ rate
I set d egual to distance walked at 5mi/h and 2d to distance walked at 8mi/hr
d/5+2d/8=135
Im lost at this point ,cant seem to see what im doing wrong
any help would be greatly appreciated
Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!

The first thing that you are doing wrong is mixing your units of measure. You converted 2 hours 15 minutes to 135 minutes, but you left your rates of speed in terms of miles per hour. If you mix apples and grapes you get fruit salad -- or what evil mathematicians shake their heads and call a wrong answer. What you need is to realize that 15 minutes is one-quarter hour, so 2 hours 15 minutes is 2.25 hours. (An alternative would be to convert the rates of speed to miles per minute -- and -- but that would make for some really ugly arithmetic)

Other than that your method works just fine.











Which is the distance walked.

Check:

If she walked 5 miles at 5 mph, then she walked for 1 hour. That means she jogged for 2.25 - 1 = 1.25 hour. 1.25 hour times 8 mph = 10 miles which is 2 times 5 miles. Answer checks.

John