SOLUTION: City A and City B are 135 km away. Two cars drove from A to B. The first car left 5 hours earlier. The second car arrived City B 30 minutes later than the first one. If the ratio o

Question 540713: City A and City B are 135 km away. Two cars drove from A to B. The first car left 5 hours earlier. The second car arrived City B 30 minutes later than the first one. If the ratio of the speed of the first to the speed of the second car is 2:5, find the speed of the first car.
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
City A and City B are 135 km away. Two cars drove from A to B.
The first car left 5 hours earlier.
The second car arrived City B 30 minutes later than the first one.
If the ratio of the speed of the first to the speed of the second car is 2:5, find the speed of the first car.
:
Let t = travel time of the 1st car
then
t - 5 + .5 = (t-4.5) is the travel time of the 2nd car (left 5 hrs later, arrived a half hr later
:
speed = dist/time
:
= the speed of the 1st car
and
= the speed of the 2nd car
the ratio of the speeds is 2:5
:

------------- =

:
Cross multiply
5 = 2
:
=
Cross multiply
675(t-4.5) = 270t
675t - 3037.5 = 270t
675t - 270t = 3037.5
405t = 3037.5
t =
t = 7.5 hrs for the 1st car to make the trip
then
7.5 - 4.5 = 3 hrs for the 2nd car.
:
Find the speed of the 1st car
= 18 mph
:
Find the speed of the 2nd car to check our solution
= 45 mph
:
See if the = ; both equal .4
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