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GRE MATH TIPS
Term | Definition |
---|---|
divisible by 2 | if last digit divisible by 2 |
divisible by 3 | if its digits add up to a multiple of 3 |
divisible by 4 | if last 2 digits are multiple of 4 |
divisible by 5 | last digit 5 or 0 |
divisible by 6 | if divisible by both 2 and 3 |
divisible by 9 | if digits add up to multiple of 9 |
GCF | break down to prime factors and what they have in common multiply together. EX 36 and 48, (2)(2)(3)(3) and (2)(2)(2)(3)(3) so (2)(2)(3)=12 |
Prime Factors Method 1 | work way up through primes. 210=2(105)=(2)(3)(35)=(2)(3)(5)(7) |
Least Common Multiple | smaller number that is multiple of both. 1) Determine prime factor 2) write out each prime number max number appears 3) multiply together to get LCM. EX) 6 & 8 6=(2)(3) 8=(2)(2)(2) so LCM is (2)(2)(2)(3)=24 |
Multiplying numbers with same base | add exponents |
Divide 2 power with same base | Keep base and subtract exponents |
Raise power to another power | multiply exponents (3^2)^4=3^8 |
Different bases same exponents | multiply bases raise to exponent |
negative exponents | 1/#^exponent |
number to 0 power | equals 1 |
fraction to a power | gives smaller number |
10 raised to an exponent | exponent dignifies number of 0s |
Positive Number Square Roots | have both a positive and negative answer |
Addition and Subtraction of Radicals | only like radicals can be added or subtracted |
Multiply and Divide Radicals | multiply or divide outside and then inside radicals |
multiplying fractions | multiply nominators and then denominators |
Dividing fractions | multiply by reciprocal of fraction after division sign |
simple interest | keep taking % of original |
compound | add for each year |
hours per unit of work | 1/a+1/b=1/T reciprocal of 1/T is answer |
combining averages | sum of terms/number of terms = x(a)+y(b)/(x+y) |
combination formula | n!/k!(n-k)! where n is number of items in group and k is number of items in each subgroup and ! means factorial (ex 5! = (5)(4)(3)(2)(1)) |
arc length | n/360 * 2pir |
area of sector | n/360*pir^2 |
lateral surface area of cylinder | 2pirh |
Total surface area of cylinder | 2pir^2+2pirh |