SOLUTION: can you help me:a jet left New York and play towards Las Vegas at an average speed of 168 miles per hour an Air Force plane left 3 hours later and flew in the same direction but wi

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Question 1175653: can you help me:a jet left New York and play towards Las Vegas at an average speed of 168 miles per hour an Air Force plane left 3 hours later and flew in the same direction but with an average speed of 240 miles per hour. how long did the jet fly before the air force plane caught up? Please and thank you.
Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


Informally....

In the 3 hours before the Air Force plane starts, the jet flies a total of 168*3 = 504 miles.

When both planes are flying, the Air Force plane catches up to the jet at a rate of (240-168)=72 mph.

The amount of time required to make up 504 miles at 72mph is 504/72 = 7 hours.

ANSWER: 7 hours

With formal algebra, you end up doing virtually the same calculations:

x = number of hours Air Force plane flies
x+3 = hours the jet flies

The distance the Air Force plane flies in x hours at 240mph is the same as the distance the jet flies in (x+3) hours at 168mph:

240x+=+168%28x%2B3%29
240x+=+168x%2B504
72x+=+504
x+=+504%2F72+=+7

ANSWER: (same as before, of course!): 7 hours