Monday, April 30, 2012
Sharing Cookies (Division by Grouping)
My son’s teacher sent out an email to parents that kids were struggling with dividing numbers equally on a recent math assessment. A little at-home practice was just what my son needed!
Forever ago, a blog follower recommended Pat Hutchins’ book The Doorbell Rang. Let’s just say, I am so glad she did! It was the perfect inspiration for this activity.
In Hutchins’ story, two children end up sharing a plate of 12 cookies with groups of children that continually ring the doorbell. Each time more kids come over, the plate of cookies is divided into equal parts to share with all the friends.
I printed a graphic of 12 oreo cookies to go along with the story. Download them here.
I put them on a platter and asked my son to count them. Then we read the first few pages of the book. When Sam and Victoria split the cookies among themselves, I wrote on a small whiteboard:
My son took the oreos and split them, placing six on the disposable plates I gave him. Then we turned the page to see that he had, in fact, divided the cookies right. (YAHOO!) When Hannah and Tom come over, the cookies must be divided up among four kids. I wrote on the whiteboard:
He split the cookies evenly and figured out 12 cookies shared by four children, meant that each would eat 3.
The story continued like this until each child at the house only gets 1 cookie. When it was done we tried a few more division problems with the cookies (12 divided by 3, 10 divided by 5, 10 divided by 2, and 9 divided by 3).
Then I put the cookies away and told him he’d have to figure out the problems without using the cookies I’d made for him. This was no easy task. I asked him how many cookies 4 children would get if the tray had 20 cookies. To help him, I wrote "1, 2, 3, and 4" on the whiteboard and had him draw cookies underneath each until all 20 cookies were represented. Ah-ha! “The answer is 5, Mom!” he exclaimed excitedly.
Now I gave him a super challenge – 35 cookies divided among 5 children. Instead of drawing circles for cookies, he made tally marks.
“Seven, Mom. Seven cookies each!!!” he yelled. I was so proud of him … almost as proud as he was of himself!