NO FLIPPING SUBTRACTION
Objective: SWBAT subtract 2-digit numbers using pictures, while remembering that numbers cannot be flipped.
Big Idea: Students love the No Flipping Subtraction rule. Can they apply it to word problems?
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Warm Ups
Yesterday I introduced the idea of NO FLIPPING subtraction. Today I start the warm up with a review of the NO FLIPPING poster and ask students what it means. I have volunteers explain why the poster is up (if the don't have enough ones, we can't just switch the numbers to subtract from the greater number of ones).
Now I put a problem on the board vertically. It is 35 - 19. I ask students how I might solve the problem? I ask for 2 volunteers to come up and show us their solution, once they have written/drawn/counted their solutions. I ask the class if they followed the No Flip Rule? We check to make sure that they didn't flip the numbers as they solved the problems.
I ask all students to solve another problem that I put on the board. I write vertically 72 - 43. I give students time to work out a solution and then we share 2 solutions. I always tell students that I know there are more solutions, but today we are only going to share a few.
I give each student a NO FLIPPING mini-poster to put in their math suitcase.
When I feel that most of the students are understanding what we are doing, I tell them that at the beginning of math today they will be trying to solve some word problems. I tell them that I will give them the problems and a separate sheet to use if they need it, to solve the problems. I tell them to use the tools in their suitcases to help them solve the problems.
Word Problems
I hand out a practice page word problems.docx. I want students to model with math (MP4), as they work to persevere in solving the problems. (MP1). I invite the children who were struggling in the warms up to bring their papers to the table where we can work together. I encourage students to draw the blocks, or to take out the actual blocks to solve the problems given.
The problems are subtraction word problems. I have put the subtraction houses on the first 3 problems. I hope that the students will put the houses on the last 3 problems on their own. I want to see how they model with mathematics for this problems (MP4).
I have students who are finished quickly work on IPAD math fact practices.
