Countdown

1. Countdown

2. What’s Happening? 1. Jamie’s family visited their grandmother, who lives 634 miles from their house. On the first day, they drove 319 miles. How many miles did they have left to drive the second day? What’s happening in this story? Can you get a picture of it in your mind? What are some representations you could use to show what’s happening? Solve this problem, and make a quick sketch that shows how you are thing about this problem.

3. Examples of sketches you may have drawn: 1 80 200 34 319 320 400 600 634 In the above sketch, the student drew a number line. She started with 319, and then made a few jumps to get to 634. First she went 1 up to 320 because that is an easy number to work with. Then she jumped to 400 and then 600 and then 34 more to 634. She then added all the jumps together to get 315. Second example: 634 ? Take Away 319 This student started at 634 and counted back 319. First she took away 300 to get 334. Then, she took away 10 to get 324 and finally 9 to get 315.

4. Subtraction Story Problems Today you’ll be solving more subtraction story problems. Read each problem carefully, and think about what’s happening in the story. You can represent each problem in the same way or try different kinds of representations. When you show your solution, make sure that your thinking is clear so that someone else can understand what you did.

5. Discussion: Strategies for Subtraction Let’s look at question #2. What representations did you use to show how you were thinking about finding the difference between 1,300 and 446 when you solved problem 2. Example Work 1300-400=900 900-40=860 860-6=854 1300-446=854 400 40 6 900 854 860 1,300

6. What’s the story? Write a story problem for each of the three subtraction problems. (You may want to split your class up and have 1/3 work on each problem)

7. Independent Work