|
As of the 2008-2009 testing year, your GRE Quantitative section might include one numeric-entry question, in which you enter a number response using the keyboard instead of selecting among multiple choices. The problem might call for you to enter a single decimal number, either positive or negative (for example, 125 or -14.2), or it might call for you to enter a fraction by typing a numerator in one box and typing a denominator below it, in another box.
Sample Numeric-Entry Question
The following numeric-entry question would be considered above-average in difficulty level; about 35% of test-takers would respond to it correctly. (The numeric-entry function is DISABLED here.)
|
If 2x + 1 is a multiple of 5, and if 2x + 1 < 100, how many possible values of x are prime numbers?
Click on the answer box, then type a number.
Backspace to erase.
|
|
Quick Tip for Sample Question
Start plugging in numbers for x that work in the equation, and keep going until you see a pattern that allows you to get to the answer as quickly as possible.
Analysis of Sample Question
Work your way up from the lowest possible value of x. Substitute numbers for x that work in the equation (numbers for which the equations holds). As you work your way up in the value of x, you should begin to see a pattern:
2(2) + 1 = 5
2(4.5) + 1 = 10
2(7) + 1 = 15
2(9.5) + 1 = 20
2(12) + 1 = 25
Notice that as the sum increase in multiples of 5, the value of x in every second equation is an integer that also increases in multiples of 5, and this integer ends in either digit 2 or 7. No integer ending in 2 (other than 2 itself) is a prime number. So you need only consider the prime number 2 along with values of x ending in 7 and less than 49 (the question stipulates that 2x + 1 < 100):
Five of these integers — 2, 7, 17, 37, and 47 — are prime numbers. Therefore, to receive credit for answering the question correctly, you must type the number 5 in the numeric-entry box.
|
|
|
