GRE math

180 degrees

• parentheses first (innermost to outer)
• exponents or radicals
• multiplication and division
• addition and subtraction

part= percent x whole

percent increase= amount of increase/ original whole x 100%

percent decrease= amount of decrease/original whole x 100%

last digit is even

sum of digits is a multiple of 3

last two digits are multiples of 4

last digit is 5 or 0

sum of digits is a multiple of 3 and last digit is even

sum of digits is a multiple of 9

last digit is 0

• sum of digits is a multiple of 3 and last two digits are a multiple of 4

average= sum of terms/ number of terms

sum=(average) x (number of terms)

B-A+1

put the numbers in numerical order and take to the middle number

take the number that appears most often

take the positive difference between the greatest and least values

probability= number of favorable outcomes/ total number of possible outcomes

an expression consisting of the sum of two or more terms

remember to reverse the inequality sign if you multiply or divide by a negative quality

the distance the number is from zero to the number on the number line, absolute value is always positive

are= 1/2 (base)(height)

two equal sides and two equal angles

three equal sides and three 60 degree angles

corresponding angles are equal and corresponding sides are proportional

• pythagorean theorum
• a²+ b²= c²

• 3:4:5
• 5:12:13
• 30 degree: 60 degree: 90 degree
• 45degree: 45 degree: 90 degree
• 1: √3: 2
• 1:1:√2

perimeter= 2(length + width)

area= (length)(width)

area= side²

area= (base)(height)

break figure into rectangle and triangle

circumference= 2(pie)r= (pie)d

area= (pie)r²

slope= rise/run= change in y/change in x

interest= (principal) x (interest rate)x time

• interest rate is expressed as decimal
• time is in years or fraction of years

(final balance)= (principal) x (1+ interest rate/C)^{(time x C)}

c= number of times compounded annually

average A per B= Total A/Total B

average speed= total distance/ time

1/r + 1/s= 1/t

• r and s are number of hours it would take two people to complete work
• t is the total time