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GMAT > Number Sense > Flashcards

Number Sense Flashcards

1
Q

Divisible by 3

A

Divisible by 3 is fhte sum of the digits is divisible by 3

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2
Q

Divisible by 9

A

Divisible by 9 is fhte sum of the digits is divisible by 9

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3
Q

Multiply a decimal with a big number

A

Trade decimal spaces 50,000 x .007 = 50 x 7

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4
Q

When multiply or divide by a negative the answer is?

A

negative

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5
Q

Prime

A

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101

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6
Q

Powers of 2

A

21=2; 22=4; 23=8; 24=16; 25=32; 26=64; 27=127; 28=256; 29=512; 210=1024

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7
Q

Powers of 3

A

31=3; 32=9; 33=27; 34=81

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8
Q

Powers of 4

A

42=16; 43=64

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9
Q

Powers of 5

A

52=25; 53=125; 54=625

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10
Q

Square roots

A

32=9; 42=16; 52=25; 62=36; 72=49; 82=64; 92=81; 102=100; 112=121; 122=144; 132=169; 142=196; 152=225

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11
Q

negativeODD

A

Negative number

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12
Q

negativeEVEN

A

Positive number

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13
Q

Y-3

A

Y-3 = 1/y3

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14
Q

Ab x Ac =

A

Ab x Ac = Ab+c

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15
Q

X0 =

A

X0 = 1

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16
Q

(Xa)b =

A

(Xa)b = Xab

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17
Q

ab/ ac =

A

ab/ ac = a b-c

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18
Q

Cube Roots

3, 4, 5

A

33 = 27; 43 = 64; 53 = 125

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19
Q

Square Roots (bigger)

A

132 =169; 142=196; 152=225; 202 =400; 252=625; 302 = 900

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20
Q

a-b =

A

a-b = 1/ab

21
Q

√ab =

A

√ab = √a x √b

22
Q

√a/b =

A

√a/b = √a / √b

23
Q

√a =

A

√a = a 1/2

24
Q

(√5) 12

when x is positive (√X) 12

A

(512) 1/2

56

when x is positive (X 12)1/2

x6

25
Q

253/2

A

√253

numerator = power

denominator = root

26
Q

Dividend = Quotient + Remainder

Divisor Divisor

A

Dividend = quotient x divisor + remainder

27
Q

take a non square root

3√216

A

take the root and divide it into prime factors

216 = 3x3x3x2x2x2 =63

28
Q

√2 ≈

√3 ≈

√5 ≈

A

√2 ≈ 1.4

√3 ≈ 1.7

√5 ≈ 2.5

29
Q

Quadratic equation

A

ax2+bx+c = 0

-b ± √b2- 4ac

2a

30
Q

to simplify a problem w/ a root in the demoninator…

A

multiple by the root

4 x √2 = 4√2 = 2√2

√2 x √2 2 .

31
Q

to simplify a deonominator with a sum or difference of a root

A

multiply by the inverse

_4 _ x 2 + √2 = 4(3√2) = 12√2

3 - √2 x 3 + √2 (3 - √2)(3 + √2) 7

32
Q

working with 2 absolute value equations

I x + 2 I < I 3x - 2 I

A

solve twice once with both having the same sign and once with one having a reversed sign

33
Q

Adding or subtracting multiples of N the result is

If N is a divisor of X and Y then

A

a multiple of N

N is a divisor of X+Y

34
Q

N is divisible by

A

the product of its primes

Primes of 72: 2, 2, 2, 3, 3

72 is also divisible by 4, 6, 8

35
Q

ODD ± ODD =

EVEN ± EVEN =

A

EVEN

36
Q

ODD ± EVEN =

A

ODD

37
Q

When multiplying if any of the integers is even the results is?

A

EVEN

38
Q

ODD divided by EVEN

A

Cannot be an integer

39
Q

Sum of two primes

A

is even unless one of the primes is 2

40
Q

Multiplying a group of numbers with an even number of negatives is ________

a group of numbers with an odd number of negatives is __________

A

Positive

Negative

41
Q

All perfect squares

A

Have an odd number of total factors

because there is a pair.

42
Q

The prime factorization of a perfect square contains…

A

The prime factorization of a perfect square contains only even powers of primes.

43
Q

N! is a multiple of

A

N! is a multiple of all integers from 1 through N

44
Q

To find the total number of factors

A

Find the prime factors and multiply the exponents

2000=24 x 53

there are 5 possible uses of 2 (0,1,2,3,4)

there are 4 possible uses of 5 (0,1,2,3)

4 x 5 = 20 there are 20 factors

45
Q

Consecutive multiples of n have Greatest Common Factor of

A

n

46
Q

weighted average

A

weight (data point) + weight (data point)…..

sum of the weight

= weighted average

47
Q

standard deviation

A

small = clustered around mean

large = spread out

Variance = square of teh standard deviation

48
Q

weighted averages with ratios

A

positive difference (x ratio) + negative difference (x ratio)

= 0

49
Q

Quant Timing

A

60 min - 7 questions

45 min - 14 questions

30 min - 21 questions

15 min - 28 questions

GMAT (5 decks)

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