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21 Cards in this Set
- Front
- Back
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Finding Sum of Symmetrical List of Numbers
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The sum from i to j inclusive =
((# of numbers) / 2 )* (i + j) ***For odd or even numbers divide twice by two. |
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Hard Math - Problem Solving
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Look for shortcut
Simplify the math |
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Hard Math - DS
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One statement is clearly suffcient, the other is weird or confusing or looks like a lot of work.
It's plain as day obvious the two stmns together are sufficient. Almost always NOT (C). (1) Alone doesn't work, (2) alone doesn't work, and you're not sure whether the two go together. Usually D. |
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Gerund
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To form a gerund, you just take a verb and add -ing. Singing, dancing, and playing are all examples of gerunds.
These are considered nouns. Usually take the possessive pronoun my. My piano teacher thinks that my playing has impoved. |
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Infinitive of a verb
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To read, to write, to sing.
Do not split the infinitive |
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Subjunctive voice - Recommend/Demand
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The first situation in which the subjunctive voice is required involves demands or recommendations. In this case, the subjunctive voice just means that an infinitive form of the main verb is used without the word to.
Any word that means demand or recommend can trigger the use of the formula. |
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Subjunctive voice - Were/Would
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The GMAT also tests a second situation that requires the use of the subjunctive voice-- the hypothetical or wish situation.
In this case, the subjunctive simply involves use of both the words were and would. Check out the above examples If I were tall, I would play basketball. |
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Group Equation
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Total = Group 1 + Group 2 + Neither - Both
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Group Grid
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Make a grid with info you know.
Complete grid by making each row, and column and add up the total. |
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Complex Math
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Use building blocks. Tackle the problem in small, manageable steps.
Know your goal. Work toward the piece(s) of information your need to answer the question. |
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Difficult Phrasing
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Translate the terms. Determine which numbers you can use.
Take small steps. work on one piece at a time. |
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Least prime number
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2
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Translating Difficult Phrasing
Even integer n is divisible by 3 |
n is multiple of 6. If n is even, that means it is a multiple of 2. You also know that it is a multiple of 3. So, it must be a multiple of 6, if it is divisible by 2 & 3.
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Translating Difficult Phrasing
Even integer q is the product of two distinct prime numbers - what about q |
q has 4 factors: q, 1, 2, and the other prime numbers. Every integer is divisible by 1. q is even, so it must be divisible by 2, which tells you that 2 is one of the prime numbers. Every integer is divisible by itself. So, q has a total of 4 factors: 1, 2, the other prime number, and q.
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Translating Difficult Phrasing
If x is the least possible product of two negative integers, what can you say about x? |
x is 1.The product of two negative numbers must be positive. To make x as small as possible, you want it to be close to 0 (since it can't be negative). The smallest x can be is (-1)(-1) = 1.
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Translating Difficult Phrasing
If m and n are each a number between -1 and 0, exclusive, what can you say about mn? |
0 < mn < 1
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Translating Difficult Phrasing
If 0 < a < 1 < b, what can be said about a^b |
0 < a^b < 1. You know that a is a faction between 0 and 1. When you multiply it by itself (b is a power greater than 1), it just get closer to 0. That means 0 < a^b < 1.
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Tricks and Traps
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Impossible problems. Look for different angle of attack.
Traps. Beware of common math mistakes. |
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Slopes of perpendicular lines
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The negative reciprocals.
For example. y = 3x + 7 the perpendicular slope is -1/3 |
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Converting time units
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Convert 230ft/40sec to miles / hour
230ft / 40 sec Then multiply by other fractions that convert the units. The units on top should cancel with the units on the bottom, leaving the desired form. 230ft/40sec X 1mile/5280ft X 60sec/1min X 60min/1hr Finally: |
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Area of Triangle inscribed in a rectangle
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The area is always half the rectangle.
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