SOLUTION: Mr. Strong started driving at 9:40 a.m. at an average speed of 60 km/h. Mr. Swift started driving from the same place at 10:10 using the same route. If Mr. Swift, took 3 hours to c

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: Mr. Strong started driving at 9:40 a.m. at an average speed of 60 km/h. Mr. Swift started driving from the same place at 10:10 using the same route. If Mr. Swift, took 3 hours to c      Log On

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Question 839267: Mr. Strong started driving at 9:40 a.m. at an average speed of 60 km/h. Mr. Swift started driving from the same place at 10:10 using the same route. If Mr. Swift, took 3 hours to catch up with Mr. Strong, at what average speed was Mr. Swift driving?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
How far did Mr Strong get from 9:40 to 10:10 ?
The time difference is: +.5+ hrs
+d%5B1%5D+=+60%2A.5+
+d%5B1%5D+=+30+ km
------------------
Let +d+ = distance Mr Swift travels until
he catches up with Mr Strong
Let +s+ = Mr Swift's average speed
Start counting time when Mr Swift leaves
-----------------------------------
Mr Swift's equation:
(1) +d+=+s%2A3+
Mr Strong's equation:
(2) +d+-+30+=+60%2A3+
---------------------
(2) +d+=+180+%2B+30+
(2) +d+=+210+
and
(1) +d+=+s%2A3+
(1) +210+=+s%2A3+
(1) +s+=+70+
Mr Swift's average speed is 70 km/hr