Divisibility Rules and Prime Numbers to 100 flashcards

Question 1

A number is divisible by 2 when what is true of its last digit?

Accepted Answer

The last digit is 0, 2, 4, 6, or 8.

Question 2

A number is divisible by 3 when what is true of the sum of its digits?

Accepted Answer

The sum of its digits is divisible by 3.

Question 3

A number is divisible by 4 when what is true of its last two digits?

Accepted Answer

The number made by its last two digits is divisible by 4.

Question 4

A number is divisible by 5 when what is true of its last digit?

Accepted Answer

The last digit is 5 or 0.

Question 5

A number is divisible by 6 when what is true of its divisibility by 2 and 3?

Accepted Answer

It is divisible by both 2 and 3.

Question 6

A number is divisible by 8 when what is true of its last three digits?

Accepted Answer

The number made by its last three digits is divisible by 8.

Question 7

A number is divisible by 9 when what is true of the sum of its digits?

Accepted Answer

The sum of its digits is divisible by 9.

Question 8

A number is divisible by 10 when what is true of its last digit?

Accepted Answer

The last digit is 0.

Question 9

What test checks whether a number is divisible by 11?

Accepted Answer

Take the alternating sum of its digits, read left to right; if that sum is divisible by 11, so is the number.

Question 10

Is 2728 divisible by 11? Use the alternating digit sum.

Accepted Answer

Yes. 2 - 7 + 2 - 8 = -11, which is divisible by 11.

Question 11

Is 31415 divisible by 11? Use the alternating digit sum.

Accepted Answer

No. 3 - 1 + 4 - 1 + 5 = 10, which is not divisible by 11.

Question 12

What is an even number?

Accepted Answer

A whole number that ends in 0, 2, 4, 6, or 8.

Question 13

What is an odd number?

Accepted Answer

A whole number that is not even.

Question 14

If a number m is a multiple of n, what do we say about m and n?

Accepted Answer

m is divisible by n.

Question 15

When is a whole number a divisible by a whole number b?

Accepted Answer

When the remainder is zero when a is divided by b.

Question 16

Is 117 divisible by 9?

Accepted Answer

Yes. Its digits add to 1 + 1 + 7 = 9, which is divisible by 9.

Question 17

Is 738 divisible by 6?

Accepted Answer

Yes. It is even, and its digit sum 7 + 3 + 8 = 18 is divisible by 3, so it is divisible by 2 and 3.

Question 18

Is 73,024 divisible by 8?

Accepted Answer

Yes. Its last three digits make 24, which is divisible by 8.

Question 19

Is 11,524 divisible by 4?

Accepted Answer

Yes. Its last two digits make 24, which is divisible by 4.

Question 20

What is a prime number?

Accepted Answer

A counting number greater than 1 whose only factors are 1 and itself.

Question 21

Is the number 1 prime, composite, or neither?

Accepted Answer

Neither. It has only one factor, itself.

Question 22

How many factors does a prime number have?

Accepted Answer

Exactly two: 1 and itself.

Question 23

What are the prime numbers less than 20?

Accepted Answer

2, 3, 5, 7, 11, 13, 17, and 19.

Question 24

What are all the prime numbers less than 100?

Accepted Answer

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97.

Question 25

Is 12 prime or composite?

Accepted Answer

Composite. Its factors are 1, 2, 3, 4, 6, and 12.

Question 26

Is 13 prime or composite?

Accepted Answer

Prime. Its only factors are 1 and 13.

Question 27

Is 21 prime or composite?

Accepted Answer

Composite. Its factors are 1, 3, 7, and 21.

Question 28

Is 37 prime or composite?

Accepted Answer

Prime. Its only factors are 1 and 37.

Question 29

Is 23 prime or composite?

Accepted Answer

Prime.

Question 30

Is 59 prime or composite?

Accepted Answer

Prime.

Question 31

Is 1,179 prime or composite?

Accepted Answer

Composite. Its digit sum is 18, so 3 and 9 are both divisors.

Divisibility Rules and Prime Numbers to 100 flashcards

The cards

How this deck was checked

Sources

Divisibility Rules and Prime Numbers to 100 flashcards

The cards

How this deck was checked

Sources

More free decks

Human body

Periodic table

Space & physics