Multiplication Strategies: Mental Math for Doubling
I’ve been working with a group of students on verbalizing their strategies for the basic multiplication facts. These students have some or many of the facts memorized, but need practice verbalizing strategies if the answer is unknown or just explaining a strategy if they do have it memorized.
All the students knew the x2 facts and used the strategy of doubling. They also used the strategy of doubling and adding one more set for the x3 facts. They could share their strategies for these facts.
When I asked how they would solve problems such as 4 x 7 or 8 x 6, they struggled with being able to verbalize a strategy. Some of them had the facts memorized. Others drew arrays or groups to solve them.
I wanted to introduce the strategy of halving then doubling, but first I wanted to make sure they had mental math strategies for doubling and halving numbers. We spent time solving problems like:
What is half of 16?
What is twice (or two times) as many as 13? Or What is 13 doubled?
Some of the students struggled with the language. When I said, “twice as many,” one student asked if she needed to “times” it. She wasn’t quite sure what she needed to do.
I also posed story problems such as:
Mrs. Pray’s class checked out 32 books one week. The second week, they checked out twice as many books. How many books did they check out the second week?
I asked the students to solve these problems mentally without writing them down. It took a little bit of practice, but with practice, the students were able to verbalize their strategies such as:
“I know 30 plus 30 is 60 and 2 plus 2 is 4. 60 plus 4 is 64, so they check out 64 books the second week.”
To read what we did next with our multiplication strategy work, go to my Blog, Multiplication Strategies: Using Doubling.
To see the Flip Flop Multiplication Decks click here, or go to the PRODUCTS page.