Prime Numbers and Divisibility Flashcards Preview

MH Arithmetic > Prime Numbers and Divisibility > Flashcards

Flashcards in Prime Numbers and Divisibility Deck (21)
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1
Q

Prime #s between 0 and 10

A

2, 3, 5 ,7

2
Q

Prime #s between 10 and 20

A

11, 13, 17, 19

3
Q

Prime #s between 20 and 30

A

23, 29

4
Q

Prime #s between 30 and 40

A

31, 37

5
Q

Prime #s between 40 and 50

A

41, 43, 47

6
Q

Prime #s between 50 and 60

A

53, 59

7
Q

Prime #s between 60 and 70

A

61, 67

8
Q

Prime #s between 70 and 80

A

71, 73, 79

9
Q

Prime #s between 80 and 90

A

83, 89

10
Q

Prime #s between 90 and 100

A

97

11
Q

Prime #s between 100 and 110

A

101, 103, 107, 109

12
Q

Divisibility by 3

A

The SUM of the integers DIGITS must be divisible by 3

13
Q

Divisibility by 4

A

The last TWO DIGITS of the number must be divisible by 4

14
Q

Divisibility by 5

A

If the integers ends in 0 or 5

15
Q

Divisibility by 6

A

Integer must be divisible by BOTH 2 and 3

16
Q

Divisibility by 8

A

The last THREE Digits of the integer must be divisible by 8 OR divisible by 2 THREE TIMES

17
Q

Divisibility by 9

A

The SUM of the integers DIGITS must be divisible by 9

18
Q

Divisibility by 10

A

the integer ends in 0

19
Q

Factor Foundation Rule: if a is divisible by ‘b’ and ‘b’ is divisible by ‘c’ -> then ‘a’ is divisible by ‘c’ as well!

A

Example: 12 is divisible by 6 and 6 is divisible by 3 –> Then 12 is also divisible by 3!

20
Q

When the GRE tells you that a number n is even –> this implies what?

A

Every even number is a multiple of 2! So n is a multiple of 2

21
Q

X is divisible by 3 and 10. Is x divisible by 45?

A

Given the information about x, we know the following prime factors: 3, 2 and 5.
Break down 45 in its prime factors: 3,3, and 5.
45 Could be a divisor but we don’t know for sure because to be sure, x must contain all the same prime factors as 45 contains!