Multiplication Facts for 2, 5, and 10
Once children feel comfortable with skip counting by 2's, 5's, and 10's, introduce the new operation of multiplication and its relationship to skip-counting. You may wish to use the lists of twos, fives, and tens as developed from the number line. Encourage children to share their thoughts and strategies as the lesson progresses.
Materials: countable objects (bottle caps, paper clips) to be placed on an overhead projector for all to see; 10 index cards per child; paper and pencil for each child
Prerequisite Skills and Concepts: Children should know how to skip-count by 2's, 5's, and 10's.
- Say: Today we will learn how to multiply. Multiplying is really not new to you. It is just a new word that makes addition easier. You can use skip-counting to learn what multiplication is all about.
Place 3 groups, with 2 paper clips in each group, on the overhead projector for all to see.
- Ask: How can we find the total number of paper clips?
Children should realize that they can count the clips by ones, skip-count by twos, or add 2 three times. Record each method on the board.
- Say: Good! You have just used addition or counting to do a multiplication problem. The total number of clips shows 3 groups, 2 in each group, or 3 times 2. We write it as "3 2 = 6." It means 3 groups of 2 equals 6.
Write 3 2 = 6 in vertical and horizontal format on the board. Note that the first factor is the number of groups and the second factor is the number in each group. (It may not be necessary to stress this difference between factors.)
- Ask: How else can we make 6?
Lead children to realize that 6 is 1 group of 6, 6 groups of 1, 2 groups of 3, or 3 groups of 2. Lead them to realize that each way represents a multiplication fact. Write each fact on the board so there are 4 math facts, each with an answer of 6.
- Ask: How can we use skip-counting to get 8? What multiplication facts are suggested by skip-counting?
Children should realize that there are 4 groups of 2, 2 groups of 4, 1 group of 8, or 8 groups of 1 in 8. Point out that skip-counting by 4's or by 2's will make 8. Show these groupings on the overhead using paper clips. Together the methods suggest 4 2 = 8, 2 4 = 8, 1 8 = 8, and 8 1 = 8. Write each multiplication fact on the board.
- Say: Look at the multiplication facts on the board. I need a volunteer to choose one fact and show how it could be written as repeated addition.
Have the volunteer write the repeated addition near the multiplication fact. Then ask the volunteer to draw a picture or diagram of the addition. Lead the volunteer to draw a diagram showing rows and columns.
- Ask: That picture is called an array. It represents repeated addition. What picture should be drawn to represent multiplication?
Children should understand that the same picture drawn to represent repeated addition is representative of multiplication.
- Ask: Who can find 2 times 6? Draw an array and hold it above your head.
After allowing time for all children to find an answer, choose several children to draw their arrays on the board. Emphasize that "two times six is twelve."
- Repeat with other multiplication facts in which two is a factor. Make sure children feel familiar with repeated addition, skip-counting, and arrays.
- Say: Now you know how to multiply. Let's write the multiplication table for twos. Start with 2 0, then find 2 1, then 2 2, and so on until 2 10. These answers are called products.
Have volunteers write the facts on the board. Ask a volunteer to explain the method used to find the product. Then distribute 10 index cards to each child. Write one fact on the front of each index card. Write the corresponding product on the back of the card. Use the cards as flash cards.
- Spend another lesson finding facts for fives. Begin by using skip-counting with fingers. For example, have 3 children hold up their fingers to find 5 6. Then continue to find the other facts for five. Be sure to review arrays, repeated addition, as well as skip-counting.
- Spend another lesson finding the facts for ten. Use children's toes in a similar strategy for skip-counting.
Wrap-Up and Assessment Hints
Multiplication needs a lot of practice. Remind children that it took time to learn the addition and subtraction facts. Have them remember how they learned those facts and apply it to the multiplication facts. Encourage the use of flash cards on a daily basis. As you assess each child, check if he/she has a clear understanding of the meaning of multiplication, through repeated addition, skip-counting, and arrays.