In the table above, what is the number of green…

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Last Updated on May 5, 2023

GMAT OFFICIAL GUIDE PS

Solution:

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

Answer: D

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