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Post subject: GMAT Symbols Posted: Sat Mar 19, 2011 5:51 pm 

Joined: Sun May 30, 2010 3:15 am Posts: 424

If a#b = ab – b + b², then 3#5 =
A. 2 B. 8 C. 15 D. 21 E. 35
(E) On test day, the # symbol or any other such symbol in a question will represent a function. In this case, a#b = ab – b + b² is a function. Simply substitute a = 3 and b = 5 into the formula and calculate: 3#5 = 3(5) – 5 + 5² = 15 – 5 + 25 = 35. The correct answer is choice (E).  Shouldn't you add before you subtract?


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Gennadiy

Post subject: Re: math (t. 2, qt.14): symbols, arithmetics Posted: Sat Mar 19, 2011 6:05 pm 

Joined: Sun May 30, 2010 2:23 am Posts: 498

Subtraction is the same as addition of the value, multiplied by (1).
15 – 5 + 25 = 15 + (5) + 25
So the order, in which you do addition and subtraction, is up to you.
POSSIBLE: 15 – 5 + 25 = (15 – 5) + 25 = 10 + 25 = 35 or 15 – 5 + 25 = 15 + (5 + 25) = 15 + 20 = 35
But if you group elements and want the "" sign to be in front of the brackets, don't forget to multiply all the terms, that go into the brackets, by 1.
WRONG: 15 – 5 + 25 = 15 – (5 + 25) = 15 – 30 = 15
RIGHT: 15 – 5 + 25 = 15 – (5 – 25) = 15 – (20) = 15 + 20 = 35


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