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Last Updated on May 10, 2024
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
