adkikani wrote:
Bunuel generis niks18 chetan2u pikolo2510 pushpitkcQuote:
how far apart will they be exactly 1.5 hours before they meet?
Is this same as:
How much distance would each have covered after 1.5 hours ?
Since I know individual speeds of both and I have total time as 1.5 hours, I can calculate total total distance by
adding individual distance traveled by each of them.The given initial total distance seems irrelevant in my approach too.
adkikani , as
pikolo2510 notes, your approach is correct and as you note, the given initial distance
IS irrelevant to your approach. Good catch. Just one question.
You say you solved for distance by using individual distance traveled. I think you solved this way:
Fanny, distance:
\((25 mph * \frac{3}{2}hrs)=\frac{75}{2}\) miles
Alexander, distance:
(65 mph * \(\frac{3}{2}hrs)=\frac{195}{2}\) miles
Add their distances: \((\frac{75}{2}mi+\frac{195}{2}mi)=\frac{270}{2}=135\) miles
If you used that method . . . what you did is the basis for adding speeds when two people travel in opposite directions. In other words, the "combined speed" approach might make a lot of sense to you.
Use whatever method works best for you. But combining speeds saves a step, avoids some weird fractions here, and on many problems can save time.
If travelers go in opposite directions, towards OR away from one another, add (combine) their speeds.
Combined speed: (25 + 65) = 90 mph
How far, total, do they travel in 1.5 hours?
Combined distance, RT=D:
(90 mph * 1.5 hrs) = 135 miles
If combining speeds does not seem as easy or intuitive as your approach, use yours!
P.S.
Bunuel , +1 for the allusion
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