Barkalarr
|
| posted on 13/11/13 at 10:01 PM |
|
|
OT : Help required - Maths Question
My son has come home with some homework tonight and I'm sure he's done this in class, but as you can expect from a typical 13 year
old..... "Teacher hasn't taught this yet". I'm a bit on the rusty side with this having not done anything like this for 20
(ish) years.
 
Description
I've taken a flyer on the question - don't take the answers in pen to be correct - this my (very lame) effort.
Here's my thought pattern.
a)
4x2 + 12 = 20
5x2 + 12 = 22
6x2 + 12 = 24
I'm really looking for one number since the question says "how much do they pay to go to each club" ???
b) - working backwards using the same formula as part a)
27-9 /3 = 6
39-9 /3 = 10
21-9 /3 = 4
** This is where I get stuck **
c)
3X + Y = 19
5X + Y = 29
8X + Y = 44
But it's asking for functions and I thought functions were f(x) ???
d) **now i'm stuck **
Can someone from the collective please explain this to me so I can pass this knowledge on to my son.....(and prove to him that dad's do actually
know EVERYTHING)
Cheers
[Edited on 13/11/13 by Barkalarr]
|
|
|
|
|
mark chandler
|
| posted on 13/11/13 at 10:20 PM |
|
|
Makes it easy looking at it like this
3x = 19-y
5x = 29-y
8x = 44-y
The answers x = 5, y = 4
Sorry I just looked at it and knew the answer
|
|
|
austin man
|
| posted on 13/11/13 at 10:21 PM |
|
|
x =5 and y=4
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
|
|
|
austin man
|
| posted on 13/11/13 at 10:22 PM |
|
|
too slow again
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
|
|
|
gremlin1234
|
| posted on 13/11/13 at 10:25 PM |
|
|
old school maths says
a: 2n + 12
b: 3n + 9
c: 5n + 4
they are all: xn + y
|
|
|
Barkalarr
|
| posted on 13/11/13 at 10:45 PM |
|
|
quote:
Originally posted by mark chandler
Makes it easy looking at it like this
3x = 19-y
5x = 29-y
8x = 44-y
The answers x = 5, y = 4
Sorry I just looked at it and knew the answer
Can one of you show me the working out please?
|
|
|
femster87
|
| posted on 13/11/13 at 11:08 PM |
|
|
Solve it as a simultaneous equation
|
|
|
SteveWalker
|
| posted on 13/11/13 at 11:09 PM |
|
|
3X + Y = 19
5X + Y = 29
8X + Y = 44
I just ignored the third line and subtracted the first line from the second, giving 2X + 0Y = 10, giving X=5.
Put the 5 back into the first line and you've got 3X + Y = 19, giving 15 + Y = 19, giving Y = 19 - 15 = 4.
|
|
|
dhutch
|
| posted on 14/11/13 at 05:37 AM |
|
|
As above, there are lots of ways of solving it, including if you have a somewhat odd mind, just looking at it until you brain goes 'well thats
easy...'
As said, there methods for solving simultaneous equations, and you actually only needs one equation per variable so as there are only tow variables
you can start of if you want be ignoring one of the three.
The other, and incorrect way of doing it when its quite simple and you expecting whole number, is just to do it by trial and error. But I cannot
recommend this as it misses the point and doesn't really do the work!
Daniel
|
|
|
liam.mccaffrey
|
| posted on 14/11/13 at 08:55 AM |
|
|
what I would do as a first pass would be rearrange 2 of the equations and make say Y the subject of the formula
3X + Y = 19 would become Y=19-3X
5X + Y = 29 would become Y=29-5X
then make them equal to one another
19-3X=29-5X
and solve for x
29-19=5x-3x
10=2x
x=5
Then plug x=5 into any of the other 3 equations for y=4
Build Blog
Build Photo Album
|
|
|
Barkalarr
|
| posted on 14/11/13 at 09:05 AM |
|
|
Thanks all... Top of the class !!
|
|
|
craig1410
|
| posted on 14/11/13 at 01:41 PM |
|
|
Here's a simple way to visualise it:
3X + Y = 19
5X + Y = 29
8X + Y = 44
The difference between the first and second expression left hand side is just 2x (5x - 3x) and this makes a difference of (29-19) = 10 on the right
hand side. So, if 2x is worth 10, then x must be worth 5 (10/2). Once you know x then you can easily work out y.
|
|
|
.jpg)
