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.

Instead of rushing to do the math (not that it is that hard, either), we can beat the clock if we just remain vigilant of the fact that any improper fraction is always greater than 1. Thus, the second term in the expression looks like an improper fraction, since the numerator is clearly greater than the denominator (the numerator is obviously greater than 3, and the denominator is less than 3).  If we added 2 (the first term of the expression) and a number greater than 1, the result must be greater than 3. We can now rule out answer choices (1), (2), (4), and (5), for none of them is greater than three.  Notice that we did NOT actually calculated the value, but ballparked it.

Ballparking can help you work your way around some tedious and time-consuming calculations in the GMAT Quant section.  Remain alert to detecting problems where you can try this approach, and consider this technique as one more option to keep in your bag of tricks.

1. Anonymous says:

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2. Anonymous says:

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CIRLES QUE A MI LO HAGAN EN ESPAÑOL
AMERICANO O EN.ITALIANO,POR FAVOR RS LA ENÉSIMA VEZ QUE LES PIDO Y NO LO HASEN LRS RUEGO ENTENDER MI SOLI
CITUD ….ATTE…Waldo Sifuentes

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