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Given that the sum of three numbers is forty-nine. The sum of the first and third...

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bevsabal | Student, Undergraduate | eNotes Newbie

Posted May 3, 2013 at 6:02 PM via web

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Given that the sum of three numbers is forty-nine. The sum of the first and third number is nine less than the second, and the third number is a quarter of the second.

Derive a system of equations representing the information given.

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tiburtius | High School Teacher | (Level 3) Associate Educator

Posted May 3, 2013 at 6:22 PM (Answer #1)

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Let's call those three numbers `x,y` and `z.` Their sum is 49 hence

`x+y+z=49`

Sum of the first and third is nine less than the second hence

`x+z=y-9`

The third is quarter of the second hence

`z=y/4`

So you have system of three equations with three variables.

`x+y+z=49`

`x-y+z=-9`

`y=4z`

Now you can solve this system by using Gauss elimination or some other method.

Your final solution is `x=51/4,` `y=29` and `z=29/4.`

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oldnick | Valedictorian

Posted May 3, 2013 at 11:32 PM (Answer #2)

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`x+y+z=49`   (1)

`x+z=y-9`     (2)

`z=1/4 y`                (3)

 

`x+y+z=49`    (4)

`x-y+z=-9`  (5)

 `z=1/4y`                (6)

 

Subtracting   (5) from (4): 

`2y=58`  `rArr y=29`

`z=29/4`

so from (1):

`x+29+29/4=49`

`x+ 145/4 =49`

`x=49-145/4=51/4`

so the solutions are:`x=51/4;y=29;z=29/4` 

 

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