Solution: To save time and improve accuracy on DS questions in GMAT, learn and apply the Variable Approach.

Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.

Visit https://www.mathrevolution.com/gmat/lesson for details.

Now we will solve this DS question using the Variable Approach.

Let’s apply the 3 steps suggested previously.

Follow the first step of the Variable Approach by modifying and rechecking the original condition and the question.

We have to find the total number of sports clubs that John and Sandy have

Let us assign a variable: Suppose John has j sports clubs and Sandy has s sports clubs.

Follow the second and the third step: From the original condition, we have 2 variables (j and s). To match the number of variables with the number of equations, we need 2 equations. Since conditions (1) and (2) will provide 1 equation each, C would most likely be the answer.

Recall 3- Principles and Choose C as the most likely answer. Let’s look at both conditions combined together.

Condition (1) tells us that John has 40 percent more sports clubs than Sandy and Condition (2) tells us that Sandy has between 5 and 11 sports clubs.

=> Converting into equation: j = s + 40%s = 1.4s and 5< s < 11

=> Since s is an integer => s must be 6, 7, 8, or 9

However,

If s = 6 => j = 1.4s => 1.4 * 6 => 8.4 cannot be the number of sports clubs that John has (∵ It’s a decimal number)

If s = 7 => j = 1.4s => 1.4 * 7 => 9.8 cannot be the number of sports clubs that John has (∵ It’s a decimal number)

If s = 8 => j = 1.4s => 1.4 * 8 => 11.2 cannot be the number of sports clubs that John has (∵ It’s a decimal number)

If s = 9 => j = 1.4s => 1.4 * 9 => 12.6 cannot be the number of sports clubs that John has (∵ It’s a decimal number)

If s = 10 => j = 1.4s =>1.4 * 10 => 14 can be the number of sports clubs that John has (∵ It’s a integer)

=> ∴ John has 14 sports clubs and Sandy has 10 sports clubs

=> Total number of sports clubs possessed by Paul and Mike: 14 + 10 = 24

The answer is unique, so the conditions combined are sufficient, according to CMT 2 - there must be only one answer.

Both conditions together are sufficient.

Therefore, C is the correct answer.

Answer: C