| Author |
Message |
Joe
science forum beginner
Joined: 16 Feb 2006
Posts: 9
|
 Posted: Tue May 23, 2006 6:51 pm Post subject:
System of Equations - Set up
|
|
|
PROBLEM 1:
A plane can travel 800 miles per hour with the wind and 720 miles per hour against the wind. Find the speed of the wind and the speed of the plain in "still" air. (Set up a system of equations and solve).
PROBLEM 2:
John leaves his house at 7:00 a.m. His sister, Mary leaves the house at 8:30 a.m. and tries to catch up with John. She is walking 2 km/h faster than him on the same route in the same direction. If they both kept on the same route, Mary could reach John 3 hours after she left. Find John and Mary's speed. (Set up a system of equations and solve). |
|
| Back to top |
|
 |
Lynn Kurtz
science forum Guru
Joined: 02 May 2005
Posts: 603
|
| Posted: Tue May 23, 2006 8:08 pm Post subject:
Re: System of Equations - Set up
|
|
|
On Tue, 23 May 2006 14:51:25 EDT, Joe <vintageheroes01@yahoo.com>
wrote:
| Quote: | PROBLEM 1:
A plane can travel 800 miles per hour with the wind and 720 miles per hour against the wind. Find the speed of the wind and the speed of the plain in "still" air. (Set up a system of equations and solve).
|
Is this a trick question? I doubt the "plain" moves at all.
Sorry, couldn't resist. More to the point, show us what you have
tried. Most of use here won't simply work your homework for you.
--Lynn
| Quote: | PROBLEM 2:
John leaves his house at 7:00 a.m. His sister, Mary leaves the house at 8:30 a.m. and tries to catch up with John. She is walking 2 km/h faster than him on the same route in the same direction. If they both kept on the same route, Mary could reach John 3 hours after she left. Find John and Mary's speed. (Set up a system of equations and solve). |
|
|
| Back to top |
|
|
matt271829-news@yahoo.co.
science forum Guru
Joined: 11 Sep 2005
Posts: 846
|
| Posted: Tue May 23, 2006 9:01 pm Post subject:
Re: System of Equations - Set up
|
|
|
Joe wrote:
| Quote: | PROBLEM 1:
A plane can travel 800 miles per hour with the wind and 720 miles per hour against the wind. Find the speed of the wind and the speed of the plain in "still" air. (Set up a system of equations and solve).
PROBLEM 2:
John leaves his house at 7:00 a.m. His sister, Mary leaves the house at 8:30 a.m. and tries to catch up with John. She is walking 2 km/h faster than him on the same route in the same direction. If they both kept on the same route, Mary could reach John 3 hours after she left. Find John and Mary's speed. (Set up a system of equations and solve).
|
Oh come on, you could show that you have made *some* effort to do your
homework! Something along the lines of: "Hi, can anyone help me with
this ... this is the question ... this is what I've tried so far ...
and I'm stuck here ...". (Even just the "Hi, can anyone help me with
this..." would be an improvement actually...) |
|
| Back to top |
|
|
Joe
science forum beginner
Joined: 16 Feb 2006
Posts: 9
|
| Posted: Tue May 23, 2006 9:11 pm Post subject:
Re: System of Equations - Set up
|
|
|
I found the answer. Could anyone verify if they are correct?
SOLUTION Problem 1:
X = speed of the wind
y = speed of plane in still air
system of eq (and use elimination method):
y = 800 - x
y = 720 + x
____________
2y = 1520
y = 760
substitute y into equation:
y = 800 - x
760 = 800 - x
x = 40
Therefore:
The speed of the wind is 40 mph
and
The speed of the plane in still air is 760 mph
SOLUTION Problem 2:
x = John's speed
x + 2 = Mary's speed
y = Distance traveled
D = r * t
system of eq:
y = (x+2)* 3
y = (x) * 4.5
symplify system of equations:
y = 3x+6
y = 4.5x
use elimination method:
y=3x+6
-1[y=4.5x]
____________
= -1.5x+6
x = 4
substitue x into equations:
Distance = y = 3x+6
=3(4)+6
=18
Mary's Speed = x+2
= 4+2
= 6
Therefore:
The Distance traveled is 18km
John's speed is 4 kmph
and
Mary's speed is 6 kmph
Thanks in advance,
Joe |
|
| Back to top |
|
|
Adam Dinwoodie
science forum beginner
Joined: 23 May 2006
Posts: 3
|
| Posted: Tue May 23, 2006 9:59 pm Post subject:
Re: System of Equations - Set up
|
|
|
Joe wrote:
| Quote: | I found the answer. Could anyone verify if they are correct?
snip
|
All looks good to me. You got the same answers as I did, anyway.
Adam |
|
| Back to top |
|
|
matt271829-news@yahoo.co.
science forum Guru
Joined: 11 Sep 2005
Posts: 846
|
| Posted: Tue May 23, 2006 10:10 pm Post subject:
Re: System of Equations - Set up
|
|
|
Joe wrote:
| Quote: | I found the answer. Could anyone verify if they are correct?
SOLUTION Problem 1:
X = speed of the wind
y = speed of plane in still air
system of eq (and use elimination method):
y = 800 - x
y = 720 + x
____________
2y = 1520
y = 760
substitute y into equation:
y = 800 - x
760 = 800 - x
x = 40
Therefore:
The speed of the wind is 40 mph
and
The speed of the plane in still air is 760 mph
SOLUTION Problem 2:
x = John's speed
x + 2 = Mary's speed
y = Distance traveled
D = r * t
system of eq:
y = (x+2)* 3
y = (x) * 4.5
symplify system of equations:
y = 3x+6
y = 4.5x
use elimination method:
y=3x+6
-1[y=4.5x]
____________
= -1.5x+6
x = 4
substitue x into equations:
Distance = y = 3x+6
=3(4)+6
=18
Mary's Speed = x+2
= 4+2
= 6
Therefore:
The Distance traveled is 18km
John's speed is 4 kmph
and
Mary's speed is 6 kmph
Thanks in advance,
Joe
|
This all looks correct to me, and very clearly laid out too. |
|
| Back to top |
|
|
Google
|
|
| Back to top |
|
|
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
Forum index
»
Science and Technology
»
Math
»
Undergraduate
