GMAT Quantitative Reasoning Practice Test 7

Question : 76 of 100

Marks: +1, -0

What was the maximum wind speed on January 1998?
(1) The average (arithmetic mean) of the maximum monthly wind speed between March 1997 and January 1998 is 35 knots, which was higher by 12 knots from the average (arithmetic mean) of the maximum monthly wind speed
betweenFebruary 1997 and December 1997.
(2) The maximum wind speed on January 1998 was 8 knots higher than the maximum wind speed on February 1997.

Statement (1) BY ITSELF is sufficient to answer the question, but statement (2) by itself is not.
Statement (2) BY ITSELF is sufficient to answer the question, but statement (1) by itself is not.
Statements (1) and (2) TAKEN TOGETHER are sufficient to answer the question, even though NEITHER statement BY ITSELF is sufficient.
Either statement BY ITSELF is sufficient to answer the question.
Statements (1) and (2) TAKEN TOGETHER are NOT sufficient to answer the question, requiring more data pertaining to the problem.

Validate

Solution:

The question doesn’t tell us much, go straight to the statements.
From statement (1) we can find the sum of the wind speeds between March 1997 and January 1998, which is

11 × 35 = 385

knots. The average of the other group of months is

11 × (35 − 12) = 253

.
The difference between the two numbers is the sum of the maximum in January 1998 and February 1997. Define J as the maximum on January and F as the maximum on February, you can write the following equation:

J + F = 385 − 253 =112

. J is what we’re looking for.
Statement (2) can be written as

J − F = 8

.
We have two simple equations with two unknowns, both statements together are sufficient.

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