DS question from GMAT PREP - III
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Assume Bob made Y items last week. Thus he made:
36 * X + (Y-36) * 1.5X - assuming Y > 36, or
36 * X - if Y <= 36
i) Bob made $480 last week
Therefore, 36 * X + (Y-36) * 1.5X = 480 - since we do not know if Y <=36 we need to consider this general case.
2 variables and one equation - not sufficient to solve
ii) Bob made 2 more items this week than he did last week and he made $510. Thus he made Y+2 items this week and,
36 * X + (Y+2-36) * 1.5X = 510.
36 * X + (Y-34) * 1.5X = 510
Again 2 variables and one equation - not sufficient to solve
But combining i) and ii), we have 2 variables and 2 unknowns. That's enough info to solve the problem. Hence C.
36 * X + (Y-36) * 1.5X - assuming Y > 36, or
36 * X - if Y <= 36
i) Bob made $480 last week
Therefore, 36 * X + (Y-36) * 1.5X = 480 - since we do not know if Y <=36 we need to consider this general case.
2 variables and one equation - not sufficient to solve
ii) Bob made 2 more items this week than he did last week and he made $510. Thus he made Y+2 items this week and,
36 * X + (Y+2-36) * 1.5X = 510.
36 * X + (Y-34) * 1.5X = 510
Again 2 variables and one equation - not sufficient to solve
But combining i) and ii), we have 2 variables and 2 unknowns. That's enough info to solve the problem. Hence C.