Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

If each of the bowlers in a tournament bowled an equal number of games, what is the average (arithmetic mean) score of all the games bowled in the tournament?

(1) 70 percent of the bowlers had an average (arithmetic mean) score of 120, and the other 30 percent had an average score of 140.

(2) Each of the 350 bowlers in the tournament bowled 3 games.

From the original condition, we need to know the total number of bowlers (n) and the total score (s). In order to match the number of variables and the number of equations, we need 2 more equations. Since both 1) and 2) each has 1 equation, there is high chance C is the answer.

(Note: This is a statistics question, one of the key questions. Also, when the condition 1) has % and the condition 2) has a number, it is likely that the condition with % is going to be the answer.)

In a case of the condition 1), since the number of bowlers is n, from (0.7n*120+0.3n*140)/n, we get a unique answer and the condition is sufficient. Therefore, the answer is A. This is a type of question that appears within the score range of 50 and 51.

From con 1) and con 2), if one of the conditions is given by numbers and the other is given by ratio (percent,fraction), then the condition with ratio (percent,fraction) value has higher chance of being the answer.

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare

The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.

Find a 10% off coupon code for GMAT Club members.

Unlimited Access to over 120 free video lessons - try it yourself

See our Youtube demo