NO FLIPPING SUBTRACTION

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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?

Warm Ups

10 minutes

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

25 minutes

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.