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GMAT Math: Strange Symbols

The GMAT often features quant questions with strange symbols. These symbols should not fluster you too much as long as you remember that they do not represent standard mathematical notation. Instead, the symbols pertain only to the problem and are defined by the GMAT (or whatever prep material you happen to be using).

Let’s have a look at a simple example:

Q prime = 3Q - 3. What is the value of (2 prime) prime?

(A) 2
(B) 3
(C) 5
(D) 6
(E) 9

 

Explanation

To approach strange symbols think of the Q’ as a recipe. To the right of the equals sign are the steps (or the recipe) you have to follow.

Another way of looking at it, whatever we see in place of Q’ we want to plug it into the ‘Q’ in 3Q - 3. Therefore 2 prime = 3(2) - 3 = 3. Because the question has two apostrophe signs, we want to repeat this procedure to get, 3 prime = 6. Answer (D).

 

This is a basic problem, one that if you saw it on the GMAT, would not bode well. So let’s try a problem that will make you sweat a little more.

A&&B = sqrt{b} - a. What the value of p in 16&&p = 9?
(A) -5
(B) 9
(C) 13
(D) 25
(E) 625

 

Explanation

Be careful not to fall the trap that switches the order of b and a. Our equation should read: sqrt{p} - 16 = 9. Solving for p:

sqrt{p} = 25
p = 625.

Answer (E).

For those who are looking to score a Q51, here are two brutally difficult questions. If you think you know the answer, go ahead and post it below with an explanation.

Brutal Question #1

x@y = 2sqrt{x} + y^2. How many unique sums of x and y result, if x@y is an integer less than 15?

(A) 9
(B) 10
(C) 21
(D) 27
(E) 30

 

Brutal Question #2

[[x]] is equal to the lesser of the two integer values closest to non-integer x. What is the absolute value of [[-pi]] + [[-sqrt{37}]]?

(A) [[9.4]]

(B) [[4 pi]]

(C) [[sqrt{99}]]

(D) [[sqrt{120}]]

(E) [[sqrt{143}]]

About the Author

Chris Lele has been helping students excel on the GRE, GMAT, and SAT for the last 10 years. He is the Lead Content Developer and Tutor for Magoosh. His favorite food is wasabi-flavored almonds. Follow him on Google+!

6 Responses to GMAT Math: Strange Symbols

  1. Farah July 21, 2014 at 5:13 pm #

    Answer to Brutal Question #2 is E.

    Since,
    -π = -3.14..
    and the non-integer -3.14 is between the integers -4 and -3. But we want the lesser;
    so [[-π]] = -4

    -√37 = -6.08..
    and the non-integer -6.08 is between integers -7 and -6. But we want the lesser;
    so [[-√37]] = -7

    Therefore, -4 + (-7) = -4 – 7 = -11, but we want the absolute value;
    so |-11| = 11

    Answer choice E is [[√143]] = [[11.95..]] = 11, since the non-integer 11.95 is between integers 11 and 12, we pick the smaller number (11) which agrees with our answer.

  2. Jeffrey Jose June 8, 2014 at 11:45 am #

    The answer to second brutal question is E

    The expression evaluates to | (-4) + (-7) | = | -11 | = 11

    The answer choice (E) comes to 11.

  3. Sebastien March 1, 2014 at 5:11 pm #

    For question 1, as Manuel said, neither x or y can be greater than 15.

    This leaves x = 0, 1, 4, 9, 16, 25, 36, 49 and y = 0, 1, 2, 3, -1, -2, -3

    The possibilities for x+y < 15 is 30. Include values x = 16 and y = -2, -3

  4. eddy January 31, 2014 at 3:57 am #

    the second Problem:

    i got a Problem, maybe you can help:
    [[-pi]] ->3,1xxx the two integeres are 3 and 4, the lesser one is 3, so -3

    [[-sqrt{37}]] -> the two integers are 6 and 7, the lesser one is 6, so -6

    the absolute sum of it is +9

    since the got only anwers with [[ ]] we have to solve for the answer which is [[ ]] = 9
    that should be the first one.

    a is the answers

    since all the others are greater that 10!

  5. Manuel August 25, 2013 at 3:49 pm #

    The answer to the first brutal question is B.

    Explanation; For the sum of x and y to be less than 15 neither part of the sum can be greater than 15. This leaves us with values of 1,2,3,4 for y and 4,9,16,25,36 for x.

    Now we just have to sum them all up and count the amount of sums that are below 15.

    • Chris Lele
      Chris Lele September 3, 2013 at 5:13 pm #

      Hi Manuel,

      Almost :). But you forgot to account for ’0′ and negative integers for ‘y’. Also, the greatest value for ‘y’ is 3, and the greatest possible value of ‘x’ is 49.

      Hope that helps!


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