Math Strategies By Gustavo Luyo

Guessing in order to find the answer to a question does not sound especially appealing if the question is one about mathematics in an international examination, let alone the GMAT quantitative section.   However, ballparking, or estimating an answer in an educated manner when solving the multiple-choice question format in the GMAT quantitative section is not as bold as it might look like.   Here we will consider a few examples that demonstrate how this technique combined with actual clever solving can give you a boost when trying to beat time-hungry GMAT math problems:

First, let’s analyze what is required to solve the problem: repeating decimals can be represented with fractions having just 9s in the denominator, for example, 0.111… = 1/9 and 0.232323… = 23/99.  We know that if the fractions in the answer choices had all of them just the digit 9 any number of times in the denominators the answer would simply be the fraction with the most 9s in the denominator.  However, what would happen if two different fractions in the answer choices had the same quantity of 9s? That would automatically invalidate such two choices, since there is no possibility of having more than one correct answer choice in the problem-solving question format.