solving with substitution new new new

tlneader

New member
Joined
Apr 2, 2006
Messages
6
New word problem:

Spike averaged 45mph driving from rochester to syracuse and 49 mph from syracuse to albany. If he drove 237 miles in 5 hours, how far is it from syracuse to albany?

x+y=237

45x+49y=5

I am having trouble solving for x. Do the equasions look correct
 
Your equations are correct. You must've entered it in wrong. My calculator gave me the right answer with the equations you have.
 
tlneader said:
Spike averaged 45mph driving from rochester to syracuse and 49 mph from syracuse to albany. If he drove 237 miles in 5 hours, how far is it from syracuse to albany?
x+y=237
45x+49y=5
I am having trouble solving for x. Do the equasions look correct

x = distance Syracuse to Albany; then distance Rochester to Syracuse = 237 - x

time S to A = x / 49
time R to S = (237 - x) / 45

Since total time = 5, then:
x / 49 + (237 - x) / 45 = 5
Solve for x
 
Hello, tlneader!

Spike averaged 45mph driving from Rochester to Syracuse and 49 mph from Syracuse to Albany.
If he drove 237 miles in 5 hours, how far is it from Syracuse to Albany?

\(\displaystyle x\,+\,y\:=\:237\)

\(\displaystyle 45x\,+\,49y\:=\:5\;\;\) . . . This is wrong
You really should name the variables first.

Let \(\displaystyle x\) = distance from Rochester to Syracuse.
Let \(\displaystyle y\) = distance from Syracuse to Albany.

Your first equation is correct.
The total distance is 237 miles: \(\displaystyle \L\,x\,+\,y\:=\:237\;\) [1]

You second equation makes no sense.
\(\displaystyle 45x\) = 45 mph times \(\displaystyle x\) miles
\(\displaystyle \;\;\)What is that? \(\displaystyle \;\)It is not the number of hours.

We have: \(\displaystyle \,\text{Distance } = \text{ Speed }\times\text{ Time}\;\;\Rightarrow\;\;\text{Time }=\;\frac{\text{Distance}}{\text{Speed}}\)

He drove \(\displaystyle x\) miles from Rochester to Syracuse at 45 mph: Time = \(\displaystyle \frac{x}{45}\) hours.
He drove \(\displaystyle y\) miles from Syracuse to Albany at 49 mph: Time = \(\displaystyle \frac{y}{49}\) hours.

Total driving time is 5 hours: \(\displaystyle \L\:\frac{x}{45}\,+\,\frac{y}{49}\:=\:5\;\) [2]


Now solve that system of equations . . .
 
Please start a new thread when you have another problem. Since you changed your problem, the calculations from the previous problem are no longer relevant.
 
No, Denis, it is not. There was an entirely different problem posted initially. The poster deleted it and posted another instead of starting a new thread. I think I will delete the post. It looks ridiculous now.
 
galactus said:
No, Denis, it is not. There was an entirely different problem posted initially. The poster deleted it and posted another instead of starting a new thread. I think I will delete the post. It looks ridiculous now.
Hey, I was JOKING!! :wink:
 
You got me. After I replied, I thought maybe you were. :oops: :lol:
 
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