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If Ferdinand, Quentin, and Zamir have a total of $28, how much money does Ferdinand have?
(1) Ferdinand has $3 less than Quentin, who has more money than Zamir does.
(2) Quentin has $5 more than Zamir, who has less money than Ferdinand does.
Source: Total GMAT Math - Jeff Sackmann
Given: Ferdinand, Quentin, and Zamir have a total of $28 Let F = the amount of money Quentin has
Let Q = the amount of money Ferdinand has
Let Z = the amount of money Zamir has
So we can write:
F + Q + Z = 28Target question: What is the value of Z Statement 1: Ferdinand has $3 less than Quentin, who has more money than Zamir does. So we can write:
F = Q - 3 (we also know that Q > Z, but that doesn't help us solve the system below)We now have the following system of equations:
F + Q + Z = 28F = Q - 3Take the top equation and replace
F with
Q - 3 to get:
(Q - 3) + Q + Z = 28Simplify to get:
2Q + Z = 31At this point, we can see that there are many different solutions to this equation, which means
there are many different possible values for ZSince we can’t answer the
target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: Quentin has $5 more than Zamir, who has less money than Ferdinand does.So we can write:
Q = Z + 5 (we also know that Z > F, but that doesn't help us solve the system below)We now have the following system of equations:
F + Q + Z = 28Q = Z + 5Take the top equation and replace
Q with
Z + 5 to get:
F + (Z + 5) + Z = 28Simplify:
F + 2Z = 23At this point, we can see that there are many different solutions to this equation, which means
there are many different possible values for ZSince we can’t answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined Statement 1 tells us that
F = Q - 3Statement 2 tells us that
Q = Z + 5When we combine this with the given information, we get the following system:
F + Q + Z = 28F = Q - 3Q = Z + 5Since we have three different linear equations with three different variables, we know we can solve this system for F, Q and
Z, which means we COULD answer the
target question with certainty (although we'd never waste valuable time on tests they doing so)
The combined statements are SUFFICIENT
Answer: C