Understanding Subtraction: Unit Review and Test
Lesson 9 of 10
Objective: SWBAT solve problems pertaining to subtraction; including word problems, determining answers for comparing numbers and take away.
The biggest problem my students have is to remember that the symbol for minus, "-", means take away. I can point out the symbol and say that is it a minus sign, but unless I say they see "take away" explicitly, they often add instead of subtract. This test is to identify who can solve subtraction equations, including word problems involving take away and comparing numbers. (1.OA.A.1, 1.OA.C.6). I will be able to plan some intervention groups based on the results of the test as we move on to our next unit. Before starting the test, my review will consist of putting a few subtraction problems on the board and have them help me solve by "take away." Also, I will do the following problems with them:
- Sam had 5 red balls. John had 3 red balls. How many more balls did Sam have?
I ask: What kind of problem is this (adding or subtracting to compare)? How do you know? ... We must draw a picture to compare the amounts and circle our partners.
- Rebecca had 8 books. She took 3 books back to the library. How many does she have now?
I ask: What kind of problem is this (adding or taking away)? How do you know? ... Let's draw a picture and mark out what went away.
When our review is finished I will set the groups up for the test. Each group will need a basket of unifix cubes or any other type of manipulative you have a large quantity of for students to use to solve problems. Go to the resource section to see pictures of the cubes ready and placed at each groups desks.
Need: Go to the resource section and print the Subtraction Unit Test, make a copy for every student.
It is important for students to be able to build models in math, to be able to think quantitatively and make sense of problems and persevere in solving. (MP 1, 2, and 4). If I am going to have my students use objects to solve their problems during daily lessons then I should also allow them to build these models to solve their problems on tests. When I administer a test, I have my students use a stand up office made from manila folders. This office serves as a cubicle for students to have their own work space and not look at neighbors work. I instruct my students to draw on the back of the test if they finish early. I do not want students walking around the room distracting each other.
Subtraction is an abstract process to complete and at this age, and many of my students are still in the concrete cognitive phase and need manipulatives to solve these kinds of problems. The resource section shows a video of a student who solves by drawing a picture; you will also see a picture of another student needing the cubes to solve his problems.