SOLUTION: A passenger train travels 392 mi in the same time that it takes a freight train to travel 322 mi. If the passenger train travels 20 mi/h faster than the freight train, find the s

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Question 175451: A passenger train travels 392 mi in the same time that it takes a freight train to
travel 322 mi. If the passenger train travels 20 mi/h faster than the freight train,
find the speed of each train.

Found 2 solutions by ankor@dixie-net.com, josmiceli:
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A passenger train travels 392 mi in the same time that it takes a freight
train to travel 322 mi. If the passenger train travels 20 mi/h faster than
the freight train, find the speed of each train.
;
Let s = speed of the freight
then
(s+20) = speed of the passenger train
:
Since the problems states the times are equal, write a time equation
Time = dist/speed
:
Pass time = freight time
392%2F%28%28s%2B20%29%29 = 322%2Fs
Cross multiply
392s = 322(s+20)
:
392s = 322s + 6440
:
392s - 322s = 6440
:
70s = 6440
s = 6440%2F70
s = 92 mph is the freight
then
92 + 20 = 112 mph is the passenger train
:
:
Check solution by finding the times of each
392/112 = 3.5 hrs
322/92 = 3.5 hrs

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
For each train:
t+=+d%2Fv
Given:
For passenger train:
t+=+392%2Fv%5Bp%5D
For freight train:
t+=+322%2Fv%5Bf%5D
(1)392%2Fv%5Bp%5D+=+322%2Fv%5Bf%5D
(2)v%5Bp%5D+=+v%5Bf%5D+%2B+20
Substitute for v%5Bp%5D in (1)
392%2F%28v%5Bf%5D+%2B+20%29+=+322%2Fv%5Bf%5D
Multiply both sides by v%5Bf%5D%2A%28v%5Bf%5D+%2B+20%29
392v%5Bf%5D+=+322%2A%28v%5Bf%5D+%2B+20%29
392v%5Bf%5D+=+322v%5Bf%5D+%2B+6440
70v%5Bf%5D+=+6440
v%5Bf%5D+=+92 mi/hr
and, since
(2)v%5Bp%5D+=+v%5Bf%5D+%2B+20
v%5Bp%5D+=+112mi/hr
check:
For passenger train:
t+=+392%2Fv%5Bp%5D
t+=+392%2F112
t+=+3.5 hrs
For freight train:
t+=+322%2Fv%5Bf%5D
t+=+322%2F92
t+=+3.5hrs
OK