# GRE Math

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1. Percent Change
(Amt change/ original amt) x 100
2. Exponent opperations
• **Need the same base**
• Multiplying exponents: add the exponents and keep the same base
• Dividing exponents: subtract the exponents and keep the same base
• Raise a power to a power: multiply the exponents
• Negative exponents: 1/exponent expression
• Fraction exponents: root of the expression

**Do NOT add or subtract exponents or roots**
3. Absolute Value
Never negative
4. Multiplying Binomials
FOIL
5. Factoring Squares
Factoring Binomials
a2 - b2 = (a-b)(a+b)

a2 +2ab + b2 = (a+b)2 a2 -2ab + b2 = (a-b)2
ax2 + bx + c = 0
7. Finding the distance between two points

Midpoint
d= sqrt (x1-x2)2 + (y1- y2)2

M= (x1+x2)/2 , (y1+y2)/2
8. Slope

Midpoint
• m=slope= rise/run
• (y1-y2) = m(x1-x2)
9. Circles and Angles (central and inscribed)
central: angle = arc

inscribed: angle = arc x2
10. Area of a triangle
(1/2)base x height
"magic x"

(3/7) + (2/9) = 7

• 3x9 = 27
• 7x2 = 14
• 41

9x7 = 63 (41/63) = 7
12. Polygons
• (3+ sides)
• sum of interior angles: (n-2)180

sum of exterior angles: 360
13. Types of triangles
• Isosceles: 2 equal sides and angles
• Equilateral: 3 equal side and angles
• Right: 90 degree angle: a2 + b2 = c2

3-4-6: 6-8-10

30-60-90: x - sqrt3 - 2x

5-12-13

45-45-90: 1 - 1 - sqrt 2
14. Parallelograms
A = base x height

supplemental angels = 180
15. Circles
Circumference: 2(pi)r

Area: (pi)r2
16. Surface area
-rectangular solid
-cube
rectangel: 2lw + 2wh + 2lh

cube: 6s2
17. Volume
-Rectangle
-Cube
-Cylinder
• Rectangle: lwh
• Cube: l3
• Cylinder: (pi)r2h
18. Trapezoid
(one pair parallel sides, one pair non-parallel)

a=(( s1 + s2)/2) xh
19. Fractions: Decimals: Percentages to Know
• (1/2) : 0.5 : 50%
• (1/3) : 0.33 : 33.3%
• (1/4) : 0.25 : 25%
• (1/5) : 0.2 : 20%
• (2/3) : 0.66 : 66%
• (3/4): 0.75 : 75%
20. Percent increase/decrease
• Percent increase: (amt of increase/original whole) x100
• Percent decrease: (amt of decrease/original whole) x100
21. How to recognize multiples
• 2: Last digit is even
• 3: Sum of digits is a multiple of 3
• 4: Last two digits are a multiple of 4
• 5: Last digit is 5 or 0
• 6: Sum of digits is a multiple of 3 and last digit is even
• 9: Sum of digits is multiple of 9
• 10: Last digit is 0
• 12: Sum of digits is a multiple of 3, and last two digits are a multiple of 4
22. Common Squared Numbers
• 1: 1
• 2: 4
• 3: 9
• 4: 16
• 5: 25
• 6: 36
• 7: 49
• 8: 64
• 9: 81
• 10: 100
• 11: 121
• 12: 144
• 13: 169
• 14: 196
• 15: 225
23. Common Square roots
• 225: 15
• 196: 14
• 169: 13
• 144: 12
• 121: 11
 Author: lsleiter ID: 40214 Card Set: GRE Math Updated: 2010-10-06 17:36:17 Tags: GRE Math Folders: Description: Formulas Show Answers: