yourstruly101
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I'm doing a practice paper and one of the questions is
Solve
6x - 5y = 110
7x + 10y = 30
Can someone give me the answer AND explain how they got it because I never understand these question and YouTube isn't helping.
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GabiAbi84
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(Original post by yourstruly101)
I'm doing a practice paper and one of the questions is
Solve
6x - 5y = 110
7x 10y = 30
Can someone give me the answer AND explain how they got it because I never understand these question and YouTube isn't helping.
...
Last edited by GabiAbi84; 4 weeks ago
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yourstruly101
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(Original post by GabiAbi84)
First :Put the first equation into terms of y.
Oh god, this just shows how bad I am at maths : (
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laurawatt
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(Original post by GabiAbi84)
First :Put the first equation into terms of y.
why? it's simultaneous equations :confused:
(Original post by yourstruly101)
Oh god, this just shows how bad I am at maths : (
so you have these
6x - 5y = 110
7x + 10y = 30

now I would multiply all of 6x - 5y = 110 by 2 then add the two equations together, the y's should cancel out and you can solve for x
then use your value for x and substitute it in to one of the equations to find y
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Shakedown
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X=13.12
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mdbdidjdksnd
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multiply 6x-5y=110 by 2 to get 12x-10y=220. Now both equations have a y multiple that can cancel out. So you do (12x-10y=220) + (7x+10y=30). So -10y+10y=0 so we can remove that leaving us with. (12x+7x)=(220+30). This is 19x=250. Divide both sides by 19 to get x=250/19. Substitute the x back in to any one of the original equations to get y. So 6(250/19)-5y=110. Expand the brackets to get (1500/19)-5y=110. Subtract both sides by 1500/19 to get -5y=590/19. Divide both sides by -5 to get y=-118/19. hope this helps
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yourstruly101
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(Original post by laurawatt)
why? it's simultaneous equations :confused:

so you have these
6x - 5y = 110
7x + 10y = 30

now I would multiply all of 6x - 5y = 110 by 2 then add the two equations together, the y's should cancel out and you can solve for x
then use your value for x and substitute it in to one of the equations to find y
So, I should time 110 x 2?
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yourstruly101
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(Original post by mdbdidjdksnd)
multiply 6x-5y=110 by 2 to get 12x-10y=220. Now both equations have a y multiple that can cancel out. So you do (12x-10y=220) + (7x+10y=30). So -10y+10y=0 so we can remove that leaving us with. (12x+7x)=(220+30). This is 19x=250. Divide both sides by 19 to get x=250/19. Substitute the x back in to any one of the original equations to get y. So 6(250/19)-5y=110. Expand the brackets to get (1500/19)-5y=110. Subtract both sides by 1500/19 to get -5y=590/19. Divide both sides by -5 to get y=-118/19. hope this helps
Yeah, this helps! Thank you
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yourstruly101
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(Original post by mdbdidjdksnd)
multiply 6x-5y=110 by 2 to get 12x-10y=220. Now both equations have a y multiple that can cancel out. So you do (12x-10y=220) + (7x+10y=30). So -10y+10y=0 so we can remove that leaving us with. (12x+7x)=(220+30). This is 19x=250. Divide both sides by 19 to get x=250/19. Substitute the x back in to any one of the original equations to get y. So 6(250/19)-5y=110. Expand the brackets to get (1500/19)-5y=110. Subtract both sides by 1500/19 to get -5y=590/19. Divide both sides by -5 to get y=-118/19. hope this helps
How did you get 19x = 250
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mdbdidjdksnd
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(Original post by yourstruly101)
How did you get 19x = 250
12x+7x is 19x. and 220+30 is 250. so the equation becomes 19x=250
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yourstruly101
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(Original post by mdbdidjdksnd)
12x+7x is 19x. and 220+30 is 250. so the equation becomes 19x=250
Oh, okay that makes sense thanks
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yourstruly101
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(Original post by mdbdidjdksnd)
multiply 6x-5y=110 by 2 to get 12x-10y=220. Now both equations have a y multiple that can cancel out. So you do (12x-10y=220) + (7x+10y=30). So -10y+10y=0 so we can remove that leaving us with. (12x+7x)=(220+30). This is 19x=250. Divide both sides by 19 to get x=250/19. Substitute the x back in to any one of the original equations to get y. So 6(250/19)-5y=110. Expand the brackets to get (1500/19)-5y=110. Subtract both sides by 1500/19 to get -5y=590/19. Divide both sides by -5 to get y=-118/19. hope this helps
I'm asking too many questions sorry but when you said divide both sides by 19 to x would that be 0.38
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mdbdidjdksnd
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(Original post by yourstruly101)
I'm asking too many questions sorry but when you said divide both sides by 19 to x would that be 0.38
so 19x/19 is just 1x. and 250/19 is 13.157... which is a long decimal so it's better to just keep it as a fraction which is 250/19. so x=250/19
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yourstruly101
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(Original post by mdbdidjdksnd)
so 19x/19 is just 1x. and 250/19 is 13.157... which is a long decimal so it's better to just keep it as a fraction which is 250/19. so x=250/19
ohhh okay thanks
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AGrizzlyBearo
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(Original post by laurawatt)
why? it's simultaneous equations :confused:
Substitution is a method of solving simultaneous equations, just maybe not the best method for this particular set of equations.
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yourstruly101
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(Original post by mdbdidjdksnd)
so 19x/19 is just 1x. and 250/19 is 13.157... which is a long decimal so it's better to just keep it as a fraction which is 250/19. so x=250/19
So I've done it and I've looked at the mark scheme to correct my work and the answer is
x= 10
y = 10
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mdbdidjdksnd
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(Original post by yourstruly101)
So I've done it and I've looked at the mark scheme to correct my work and the answer is
x= 10
y = 10
could it be that you posted the question wrong?
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davros
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(Original post by yourstruly101)
So I've done it and I've looked at the mark scheme to correct my work and the answer is
x= 10
y = 10
Those values don't satisfy the equations you posted originally!

Can you upload a picture of the question?
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yourstruly101
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(Original post by davros)
Those values don't satisfy the equations you posted originally!

Can you upload a picture of the question?
I used the site onmaths
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