My classmates and I were uncertain about an answer on one of our math tests. The question was this: There are two cars; the first car goes 45 miles per an hour. The second car goes 30 miles per an hour. How many hours will it take for both cars to have the same speed if the second car goes ahead by 1 hour?
I got 3 hours as my answers. My classmates got about 2 hours or @ hours and 45 minutes. Which one is correct?
2007-03-30 15:11:23 · 8 answers · asked by <3 2 in Science & Mathematics ➔ Mathematics
Sorry, the @ sign was supposed to be 2
2007-03-30 15:11:53 · update #1
Thanks its_victoria08. I worded my question wrong, sorry.
How many hours will it take for both cars to be at the same point if the second car goes ahead by 1 hour?
2007-03-31 13:10:12 · update #2
Car 2 travels x+1 hours, while car 1 travels x hours
45x = 30(x+1)
45x = 30x + 30
15x = 30
x = 2
They will be at the same point two hours after car 1 starts.
Another way of saying it, they'll be at the same point three hours after car 2 starts.
2007-03-30 15:16:47 · answer #1 · answered by Steve A 7 · 0⤊ 0⤋
Well, if one care is going 45 miles per hour, and the second is going 30 miles per hour, they'll never be going the same speed.
I'm sure you probably meant "How many hours will it take for both cars to be at the same point if the secondhour goes ahead by 1 hour?"
According to the way you asked this question, my answer is correct. :P
2007-03-30 22:31:04 · answer #2 · answered by its_victoria08 6 · 1⤊ 0⤋
In 1 hour, the second car will have traveled 30 miles...it has a 30 mile head start. Constant velocity can be expressed as a linear equation of distance over time.
1st car: y = 45x
2nd car: y = 30x + 30
We add 30 to the second car since it has a head start. Now, we must set these equations equal to one another to find a value of time.
45x = 30x + 30
5x = 30
x = 2
So in 2 hours, the first car will catch up. You can check by plugging in values.
In three hours (including the 1 hour head start), the second car travels 90 miles. In 2 hours, the first car also travels 90 miles.
2007-03-30 22:17:37 · answer #3 · answered by Bhajun Singh 4 · 0⤊ 0⤋
after one hour when car 2 started to move
car 2 has travelled 30 miles
car 1 hasn't moved yet
after 2 hours when car 2 started to move
car 2 has travelled 60 miles
car 1 has travelled 45 miles
after 3 hours when car 2 started to move
car 2 has travelled 90 miles
car 1 has travelled 90 miles
2007-03-30 22:25:36 · answer #4 · answered by M. Abuhelwa 5 · 1⤊ 0⤋
1st car: y = 45x
2nd car: y = 30x + 30
We add 30 to the second car since it has a head start. Now, we must set these equations equal to one another to find a value of time.
45x = 30x + 30
5x = 30
x = 2
So in 2 hours, the first car will catch up. You can check by plugging in values.
2007-03-30 22:19:44 · answer #5 · answered by Anonymous · 0⤊ 0⤋
the 2 hours is right
2007-03-30 22:22:00 · answer #6 · answered by Prof.G 1 · 0⤊ 0⤋
30miles/hour X 1 hour = 30 miles
45 miles/hour
30miles + 30miles/hours X t hours =0 + 45miles/hour X t hours
30+30t = 45t
t=2 hours
2007-03-30 22:23:45 · answer #7 · answered by mradigan747 2 · 0⤊ 0⤋
v1*t1=v2*t2
45*t1=30*(t1+1)
45t1=30t1+30
15t1=30
t1=2
So, it takes 2 hours for both cars to have the same speed.
2007-03-30 22:20:00 · answer #8 · answered by aaaaa 2 · 0⤊ 0⤋