Question

Help with extended proportion?
x : y : z = 2 : 3 : 7 ; 4x + 5y - 3z = 6
x/2 = y/3 = z/7 (=k)

x/2 = k ; x = 2k
y/3 = k ; y = 3k
z/7 = k ; z = 7k

2k + 3k + 7k = 6
12k = 6

k= ?
Did I do something wrong?

Answer 1

Yes you did x+y+z=6 instead of 4x+5y-3z=6 i.e. incorrect substitution

Answer 2

I have to find the value of k before doing 2*k = x ; k*3 = y ; k*7 = z then I can use the values of those to substitute in the equation. I do not have k yet.

Answer 3

You substituted x=2k, y=3k, z=7k into x+y+z=6 instead of 4x+5y-3z=6

Answer 4

Here is an example of what my professor has done.

x : y : z : t = 1 : 2 : 3 : 4
x+y+z+t = 190.

x/1 = k, x= k
y/2 = k, y = 2k
z/3 = k; z=3k
t/4 = k; t=4k

k + 2k + 3k + 4k = 190
10k = 190
k = 19

Now k*1 = 19 so x = 19
2*19 = 38 -> y = 38
3*19 = 57 so z = 57
4*19 = 76 so t = 76

that is why :
19 + 38 + 57 + 76 = 190.

Answer 5

Because the equation was x+y+z+t=190

Answer 6

Now the equation is 4x+5y-3z=6

Answer 7

He was substituting x=k,y=2k,z=3k,t=4k into x+y+z+t=190

Answer 8

Yes but the question I am doing I HAVE NOT FOUND K yet therefore I DID NOT substitute ANYTHING yet.

Answer 9

how would I find k? do I have to multiply 2k by 4 or?

Answer 10

Then explain to me how you got 2k + 3k + 7k = 6

Answer 11

I probably have forgot to multiply them?

Answer 12

Exactly

Answer 13

so this means 2k * 4
3k*5 and 7k * 3??

Answer 14

Yes

Answer 15

Ohhh now i get it! thank you! let me see if I can get the correct answer now

Answer 16

No problem :)

Answer 17

x=6,y=9,z=21

Answer 18

http://www.wolframalpha.com/input/?i=4x+%2B+5y+-+3z+%3D+6%3B+x%2F2+%3D+y%2F3+%3D+z%2F7

Answer 19

I got the answer! :D

Answer 20

Glad you got the answer

Answer 21

Yep i did another question the same and got it too :D