During rush hour, Fernando can drive 40 miles using the side roads in the same time that it takes to travel 30 miles on the freeway. If Fernando's rate on the side roads is 7 mi/h faster than his rate on the freeway, find his rate on the side roads.
2007-03-26 13:46:33 · 2 answers · asked by DEE L 2 in Science & Mathematics ➔ Other - Science
Imagine I told you up front that the answer is X miles/hr.
Now how would you check that this is correct?
You should plug in X to the freeway and the side roads and make sure that they both take the same amount of time, right?
Time for side road = 40 mi / X
Time for freeway = 30 mi / (X-7)
Once you plug in X, you should get the same time for both of these equations.
Since I don't yet know X, let's set them equal and solve for X.
40/X = 30/(X-7)
40 = 30X/(X-7)
40(X-7) = 30X
40X - 280 = 30X
10X = 280
X = 28 mi/hr
Now plug in 28 mi/hr into the equations and make sure you 1.428 hours for both. You do!
2007-03-26 14:02:07 · answer #1 · answered by Andy C 2 · 1⤊ 0⤋
Greek is more simple.........
2007-03-27 14:58:44 · answer #2 · answered by vivet 7 · 0⤊ 0⤋