Question 1133365: two cars leave the same place at the same time traveling in the same direction for 3 hours. the first car travels twice as fast as the second car. how fast is the second car traveling if they are 90 miles apart when they stop?
Found 4 solutions by Boreal, ankor@dixie-net.com, greenestamps, josgarithmetic:
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! second car's speed=x mph
first car's speed=2x mph
The difference in speed is x mph (2x-x)
In 3 hours, they are 90 miles apart, so the difference is 90 mi/3h or 30 mph
The difference is also the second car's speed, x, or 30 mph ANSWER
The first car is traveling 60 mph, twice as fast. In 3 hours, they are 90 miles apart
Answer by ankor@dixie-net.com(22740)  (Show Source):
You can put this solution on YOUR website! two cars leave the same place at the same time traveling in the same direction for 3 hours.
the first car travels twice as fast as the second car.
how fast is the second car traveling if they are 90 miles apart when they stop?
:
let s = speed of the 2nd car
then
2s = speed of the 1st
:
write a distance equation, dist = speed * time
1st dist - 2nd car dist = 90 mi
2s(3) - s(3) = 90
simplify, divide equation by 3
2s - s = 30
s = 30 mph is speed of the 2nd car
:
:
Check this: find the actual distances each travels
60 * 3 = 180 mi for the 1st car
30 * 3 = 90 mi for the 2nd
------------------------------
difference: 90 mi
:
Answer by greenestamps(13198)  (Show Source):
You can put this solution on YOUR website!
You have received two responses showing different ways to solve the problem algebraically; there are many others.
But unless an algebraic solution is required, algebra is overkill for this problem; it is easily solved with logical reasoning and a bit of simple mental arithmetic.
If the two cars are traveling for the same amount of time and the first car travels twice as fast as the second, then the first car travels twice as far as the second.
If after 3 hours the 2 cars are 90 miles apart, that means the second car has gone 90 miles and the first car has gone 180 miles. So the slow car is traveling at 90/3 = 30mph and the fast car is traveling at 180/3 = 60mph.
Answer by josgarithmetic(39616)  (Show Source):
|
|
|
