Question: G can copy 50 pages in 8 hrs, and S copy 50 pages in 6 hours. to copy 100 page together, they will use how many hours?
===>> (50/8+50/6)*time=100
Question: G drives 50 miles in 8 hrs, and S drives 50 miles in 6 hrs. To drive 100 miles together, they will use how many hours?
It seems like we can combine rates, but we cant do the same thing for average speed? Can anyone explain to me why?
Thanks a lot.
rate and average questions
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- simplyjat
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What do you mean by driving together?. In English it means each one drives 100 miles....lalabee wrote:To drive 100 miles together
simplyjat
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How is the second question about average speed?lalabee wrote:Question: G can copy 50 pages in 8 hrs, and S copy 50 pages in 6 hours. to copy 100 page together, they will use how many hours?
===>> (50/8+50/6)*time=100
Question: G drives 50 miles in 8 hrs, and S drives 50 miles in 6 hrs. To drive 100 miles together, they will use how many hours?
It seems like we can combine rates, but we cant do the same thing for average speed? Can anyone explain to me why?
Thanks a lot.
The question itself is a bit amibiguous, but assuming that you mean "how long will it take them to drive a total of 100 miles", you'd solve it the exact same way as you did the first example.
50m/8h = 25/4 mph
50m/6h = 25/3 mph
combined rate = 25/4 + 25/3 = 6.25 + 8.33 = approx 14.6mph total
100/14.6 = some ugly number under 7, but that's the answer.
Average speed questions are different that total speed questions.
Stuart Kovinsky | Kaplan GMAT Faculty | Toronto
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