Factors
List all of the factors for 12.
1, 2, 3, 4, 6, 12
What is the definition for a prime number?
A whole number that can be divided evenly only by 1, or itself. It has exactly two factors.
Which of the following are divisible by 2?
4; 8; 11; 15; 18; 20; 27
What do they all have in common?
4; 8; 18; 20;
All are even numbers.
Beth was helping Mrs. Williams in the library. There were 36 total books that needed to be placed on four shelves. If there were an equal number of books on each shelf, how many books would be on each shelf?
Write a number sentence. Use a variable for the unknown. Solve for the unknown.
4 x A = 36
A = 9
Mrs. Smith made 42 cookies and she divided them equally among her friends. If each friend received six cookies, how many friends did Mrs. Smith give cookies to?
Write a number sentence using a variable for the unknown. Solve.
42 / A = 6
A = 7
Draw all arrays for 8. Write a number sentence for each array.
8 x 1
1 x 8
2 x 4
4 x 2
What is the definition for a composite number?
A whole number that can be divided evenly by 3 or more factors.
Which of the following numbers are divisible by 3?
3; 11; 13; 15; 21; 42
How do you know?
3; 15; 21; 42
Amy and Kim rode their bikes on Saturday in the park. Amy rode for 7 minutes. Kim rode four times as many minutes as Amy. How many total minutes did Kim ride her bike?
Write a number sentence and use a variable for the unknown. Solve for the unknown.
4 x 7 = 28 minutes
Write both a multiplication and division sentence for the following. Use a variable for the unknown. Solve for the unknown. There were eight deer standing in the garden on Saturday morning. Saturday evening there were two times as many deer in the garden than there were in the morning. How many deer were in the garden in the evening?
2 x 8 = A
A = 16 deer
Write all factor pairs for 24.
1 x 24
2 x 12
3 x 8
4 x 6
What do 5, 11, 13, and 17 have in common?
Explain your answer.
They are all prime numbers.
They each only have two factors.
Identify the numbers that are divisible by 5.
10; 25; 33; 47; 60; 105
How do you know these numbers are divisible by 5?
10; 25; 60; 105
If the ones place is 5 or 0, 5 is the hero.
Kate has 7 humming bird feeders in her back yard. When she looked out early in the morning she counted seven humming birds on each feeder. How many humming birds were there altogether?
Write a number sentence with a variable for the unknown. Solve for the unknown.
7 x 7 = A
A = 49 humming birds
A family made 24 cookies for a bake sale. They are deciding how many cookies to put in each bag so that all the bags have an equal number of cookies.
The family lists the factor pairs of 24 to determine all the possible ways to divide the cookies into bags. List all the factor pairs of 24. Explain your answer.
1 x 24
2 x 12
3 x 8
4 x 6
List all of the factors for 16.
1, 2, 4, 8, 16
Write the factors for 17.
Is 17 prime or composite?
1, 17
prime
Is 30 divisible by 2? 3? 4? 5? 6? 9? 10?
2, 3, 5, 6, and 10
It took Chip 5 minutes to solve 70 multiplication problems. It took Scott four times as long as Chip. How many minutes did it take Scott to solve 70 multiplication problems?
Write a number sentence using a variable for the unknown. Solve for the unknown.
4 x 5 = A
A = 20 minutes
A family made 25 cookies for a bake sale. They are deciding how many cookies to put in each bag so that all the bags have an equal number of cookies.
The family decides to eat 9 cookies before they put the remaining cookies in the bags. Will they be able to put all the remaining cookies in 5 bags and still have an equal number in each bag? Explain why or why not using what you know about factor pairs.
No
25 - 9 = 16 cookies
5 bags
16 / 5 = 3 cookies for each bag. One cookie left over.
How do you know the number 20 is a composite number?
It is an even number and it ends in 0.
Is 17 divisible by 2? 3? 4? 5? 6? 9? 10?
None of them.
Write a number sentence for 9 groups of 3 is 27.
9 x 3 = 27
Write a number sentence using a variable for the unknown. Solve for the unknown.
Mary was making hair bows for her friends. She used 8 yards of blue ribbon. That is two times the amount of pink ribbon. How many yards of pink ribbon did she use?
2 x A = 8
A = 4 yards of pink ribbon