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In the table above, what is the number of green marbles in J

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In the table above, what is the number of green marbles in J  [#permalink]

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01 Oct 2012, 04:11
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Difficulty:

5% (low)

Question Stats:

91% (01:44) correct 9% (02:05) wrong based on 807 sessions

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In the table above, what is the number of green marbles in Jar R ?

(A) 70
(B) 80
(C) 90
(D) 100
(E) 110

Practice Questions
Question: 55
Page: 159
Difficulty: 600

Attachment:

Table.png [ 40.01 KiB | Viewed 16125 times ]

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Re: In the table above, what is the number of green marbles in J  [#permalink]

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01 Oct 2012, 04:11
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SOLUTION

In the table above, what is the number of green marbles in Jar R ?

(A) 70
(B) 80
(C) 90
(D) 100
(E) 110

We need to find the value of $$z$$, while given that:

$$x+y=80$$;
$$y+z=120$$;
$$x+z=160$$.

Sum these 3 equations: $$2x+2y+2z=360$$ --> reduce by 2: $$x+y+z=180$$ --> since we know that $$x+y=80$$, then $$80+z=180$$ --> $$z=100$$.

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Re: In the table above, what is the number of green marbles in J  [#permalink]

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01 Oct 2012, 04:19
2
To solve, I took the sum of the expressions as seen below:

X + Y = 80
Y + Z = 120
X + Z = 160
2X + 2Y + 2Z = 360

Dividing by 2 we get X + Y + Z = 180.

Since we know X + Y = 80 from Jar P, we can deduce that Z = 100. Since Z is the number of green marbles in Jar R we have our solution.

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Re: In the table above, what is the number of green marbles in J  [#permalink]

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01 Oct 2012, 19:22
1
x+y = 80 ---(1)
x+z = 160---(2)
z+y= 120---(3)
Subtract equation 1 from 2 & we get--> z-y = 80----(4)
Add equation (4) & (3) we get--> 2z= 200
z=100
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Re: In the table above, what is the number of green marbles in J  [#permalink]

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03 Oct 2012, 23:41
1
x + y = 80 ......(1)
y + z = 120 .....(2)
x + z = 160 ......(3)

From (2) above, z=160-y .....Substitute value of z in (3)

==> x-y = 40 ....(4)

Solve (1) and (4), to get x = 60
==> y = 20
==> z = 100

Thus, number of green marbles in Jar R = 100 (Ans = D)
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Re: In the table above, what is the number of green marbles in J  [#permalink]

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04 Oct 2012, 13:20
2
SOLUTION

In the table above, what is the number of green marbles in Jar R ?

(A) 70
(B) 80
(C) 90
(D) 100
(E) 110

We need to find the value of $$z$$, while given that:

$$x+y=80$$;
$$y+z=120$$;
$$x+z=160$$.

Sum these 3 equations: $$2x+2y+2z=360$$ --> reduce by 2: $$x+y+z=180$$ --> since we know that $$x+y=80$$, then $$80+z=180$$ --> $$z=100$$.

Kudos points given to everyone with correct solution. Let me know if I missed someone.
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Re: In the table above, what is the number of green marbles in J  [#permalink]

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10 Dec 2012, 03:43
$$x + y = 80$$ eq 1
$$y + z = 120$$ eq 2
$$x + z = 160$$ eq 3
______________
$$2x + 2y + 2z = 360 --> x + y+ z = 180$$ eq 4

Combine eq 4 and eq 1:

$$80 + z = 180 --> z = 100$$

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Re: In the table above, what is the number of green marbles in J  [#permalink]

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13 Apr 2014, 07:52
Bunuel wrote:
SOLUTION

In the table above, what is the number of green marbles in Jar R ?

(A) 70
(B) 80
(C) 90
(D) 100
(E) 110

We need to find the value of $$z$$, while given that:

$$x+y=80$$;
$$y+z=120$$;
$$x+z=160$$.

Sum these 3 equations: $$2x+2y+2z=360$$ --> reduce by 2: $$x+y+z=180$$ --> since we know that $$x+y=80$$, then $$80+z=180$$ --> $$z=100$$.

Kudos points given to everyone with correct solution. Let me know if I missed someone.

Are we always allowed to sum the 3 equations? Do we need to have some commonalities to be able to sum the equations?
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Re: In the table above, what is the number of green marbles in J  [#permalink]

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13 Apr 2014, 20:16
X+Y =80 --------- (1)

Y+Z =120 -------- (2)

X+Z =160 -------- (3)

Subtract (3) -(1)

we get

Z - Y = 80 -----------(4)

Z=100;

Hence D.
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Posts: 51229
Re: In the table above, what is the number of green marbles in J  [#permalink]

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14 Apr 2014, 00:30
russ9 wrote:
Bunuel wrote:
SOLUTION

In the table above, what is the number of green marbles in Jar R ?

(A) 70
(B) 80
(C) 90
(D) 100
(E) 110

We need to find the value of $$z$$, while given that:

$$x+y=80$$;
$$y+z=120$$;
$$x+z=160$$.

Sum these 3 equations: $$2x+2y+2z=360$$ --> reduce by 2: $$x+y+z=180$$ --> since we know that $$x+y=80$$, then $$80+z=180$$ --> $$z=100$$.

Kudos points given to everyone with correct solution. Let me know if I missed someone.

Are we always allowed to sum the 3 equations? Do we need to have some commonalities to be able to sum the equations?

Yes, we can sum/subtract/multiply equations. I think you are mixing equations with inequalities, for which there are specific rules.

Hope this helps.
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Re: In the table above, what is the number of green marbles in J  [#permalink]

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28 Apr 2014, 20:27
Bunuel wrote:
russ9 wrote:
Bunuel wrote:
SOLUTION

In the table above, what is the number of green marbles in Jar R ?

(A) 70
(B) 80
(C) 90
(D) 100
(E) 110

We need to find the value of $$z$$, while given that:

$$x+y=80$$;
$$y+z=120$$;
$$x+z=160$$.

Sum these 3 equations: $$2x+2y+2z=360$$ --> reduce by 2: $$x+y+z=180$$ --> since we know that $$x+y=80$$, then $$80+z=180$$ --> $$z=100$$.

Kudos points given to everyone with correct solution. Let me know if I missed someone.

Are we always allowed to sum the 3 equations? Do we need to have some commonalities to be able to sum the equations?

Yes, we can sum/subtract/multiply equations. I think you are mixing equations with inequalities, for which there are specific rules.

Hope this helps.

Thanks for clarifying.

Just to confirm one of your comments above -- "Yes, we can sum/subtract/multiply equations." -- would this be valid for the problem even if one of the equations didn't have any common variables. What I mean is, if the equations read:

$$x+y=80$$;
$$a+b=120$$;
$$x+z=160$$.

Can we still add the 3?
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Posts: 51229
Re: In the table above, what is the number of green marbles in J  [#permalink]

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28 Apr 2014, 23:58
russ9 wrote:
Bunuel wrote:
russ9 wrote:
Are we always allowed to sum the 3 equations? Do we need to have some commonalities to be able to sum the equations?

Yes, we can sum/subtract/multiply equations. I think you are mixing equations with inequalities, for which there are specific rules.

Hope this helps.

Thanks for clarifying.

Just to confirm one of your comments above -- "Yes, we can sum/subtract/multiply equations." -- would this be valid for the problem even if one of the equations didn't have any common variables. What I mean is, if the equations read:

$$x+y=80$$;
$$a+b=120$$;
$$x+z=160$$.

Can we still add the 3?

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Re: In the table above, what is the number of green marbles in J  [#permalink]

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09 Sep 2014, 21:05
The table provided in this question was a boon for me. See how below.....
Attachment:

Table.png [ 45.65 KiB | Viewed 11031 times ]

1. Replaced y with (80-x). The equation remains intact on "Jar P" row

2. Copied (80-x) in "Jar Q" row.

These 2 steps directly eliminates x & y

3. Adding rows "Jar Q" & "Jar R"

2z+80 = 280

z = 100

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Re: In the table above, what is the number of green marbles in J  [#permalink]

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21 Nov 2014, 02:28
From the given table we could make equations like
Equation 1. Given x+y=80 ----> x=80-y
Equation2. Given y+z=120
Equation3. Given x+z = 160
Substituting the value of x in Equation 3 from Equation 1
Equation 4. (80-y)+z=160 ----> -y+z = 80
Adding Equation 2 and Equation 4
2z=200 ---> Z=100.
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Re: In the table above, what is the number of green marbles in J  [#permalink]

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22 Jul 2015, 08:52
just substract from the first equation the 2nd and the 3rd you'll get --> x+y-y-z-x-z = -200 ->x,y cancel out and Z=100 (D)
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In the table above, what is the number of green marbles in J  [#permalink]

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30 May 2016, 04:32
Bunuel wrote:

In the table above, what is the number of green marbles in Jar R ?

(A) 70
(B) 80
(C) 90
(D) 100
(E) 110

We can create three equations from the information presented in the table.

Equation 1: x + y = 80

Equation 2: y + z = 120

Equation 3: x + z = 160

These equations present us with a good opportunity to use the “combination method” to solve multiple equations. Here, we can add equations together. Because we need the number of green marbles in jar R, we need to determine the value of z.

We can start by multiplying equation 1 by -1.

-1(x + y = 80) = -x – y = -80

Next, we add this equation to equation 2. So we have:

-x - y = -80 + (z + y = 120) = z – x = 40

Now we can add z – x = 40 to equation 3. So we have:

–x + z = 40 + (x + z = 160)

2z = 200

z = 100

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Re: In the table above, what is the number of green marbles in J  [#permalink]

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30 May 2016, 05:03
Bunuel wrote:

In the table above, what is the number of green marbles in Jar R ?

(A) 70
(B) 80
(C) 90
(D) 100
(E) 110

Practice Questions
Question: 55
Page: 159
Difficulty: 600

Attachment:
Table.png

Simply add the three given details

x+y=80
y+z=120-
x+z=160

2(x+y+z) = 360
x+y+z = 180

Now We want green marbles in Jar R. That is we want z.
x+y+z=180
x+y= 80; this means z = 100
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Re: In the table above, what is the number of green marbles in J  [#permalink]

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22 Feb 2018, 12:38
Hi All,

Complex-"looking" prompts can often hide hidden patterns that will help you to reduce the amount of work you need to do to answer the question.

The question asks us for the number of green marbles in Jar R, so we're asked "what is the value of Z?"

In the table, you might notice that each variable shows up EXACTLY TWICE, so if we add all of the equations together, we have…

2X + 2Y + 2Z = 360

So…

X + Y + Z = 180

Notice in Jar P….X + Y = 80

Combining these two equations gives us the value of Z…..100

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Re: In the table above, what is the number of green marbles in J &nbs [#permalink] 22 Feb 2018, 12:38
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