SOLUTION: A bus entered the Interstate and traveled at a constant speed of 42 mph. Two hours later a second bus followed the first bus, entering the Interstate from the same point as the fir

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Question 476024: A bus entered the Interstate and traveled at a constant speed of 42 mph. Two hours later a second bus followed the first bus, entering the Interstate from the same point as the first bus, and traveled at a constant speed of 66 mph. How long will it take the second bus to catch up with the first bus?
Found 2 solutions by jorel1380, josmiceli:
Answer by jorel1380(3719) About Me  (Show Source):
You can put this solution on YOUR website!
42x2=84
42p+84=66p
24p=84
p=84/24=3.5 hours before the second bus catches up..

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
How many miles head start does the 1st bus have?
+d%5B1%5D+=+42%2A2+
+d%5B1%5D+=+84+ mi
Start a stopwatch when the 2nd bus enters interstate.
Both will now travel for the same amount of time
until bus 2 catches bus 1. Call this time t.
---------------------
Let d = distance bus 2 has to go to catch bus 1
For bus 2:
(2) +d+=+66t+
For bus 1:
(1) +d-+84+=+42t+
----------------
Substitute d in (2) for d in (1)
(1) +66t+-+84+=+42t+
(1) +24t+=+84+
(1) +t+=+3.5+
It takes the 2nd bus 3.5 hrs to catch 1st bus
check:
(2) +d+=+66t+
(2) +d+=+66%2A3.5+
(2) +d+=+231+
and
(1) +d+-+84+=+42t+
(1) +231+-+84+=+42%2A3.5+
(1) +147+=+147+
OK