kfrohnapfel said:
Two planes leave an airport traveling in opposite directions. One plane travels at 470 km per hour and the other at 430 km per hour. How long will it take them to be 2250 km apart?
I know the formula is d=rt but the opposite directions part is confusing me
Maybe it might help if we draw a diagram.....the airport is between the two planes, which are traveling in opposite directions:
A............................................Airport..............................B
Suppose Plane A is the one traveling at 470 km/hr, and Plane B is the one traveling at 430 km/hr.
They leave at the same time (apparently), so they'll be traveling for the same amount of time. Let t be the number of hours they each travel.
You are correct in thinking that the formula you need to use is d = r*t.....
For plane A, r = 470, and t is the number of hours traveled. So, for Plane A, d = 470t
For Plane B, r = 430, and t is the number of hours traveled. For Plane B, d = 430t.
Let's put those distances into the diagram:
A............................................Airport..............................B
<------------------470t-----------------------><--------------430t-------------->
<--------------------------------------2250 km----------------------------------->
Do you see that if we ADD the distances traveled by the two planes, we should get the total distance between them?
470t + 430t = 2250
Solve that for t....the time that each plane travels.
(Note to BigGlenn......isn't it better to give some explanation than just an answer??)
