2. MENTAL MATH

3. Subtracting Tens and Compensate Strategy: When subtracting numbers ending in 7, 8, or 9, round that number to the nearest tens and then add on 3, 2, or 1 to the answer. Example: 75 – 57 75 – 60 = 15 + 3 = 18

4. Practice with…. Subtracting using Tens…

5. 64 - 38 64 – 40 = 24 +2 = 26

6. 49 - 28 49 – 30 = 19 + 2 = 21

7. 91 - 57 91 – 60 = 31 + 3 = 34

8. 74 - 49 74 – 50 = 24 + 1 = 25

9. 65 - 39 65 – 40 = 25 + 1 = 26

10. Timed Quiz Beginning with the next slide you will have 10 seconds to answer each question using the mental math strategy just practiced. There will be 10 questions to do. Put the title “Mental Math” at the top of your page, your name to the right, and then numbers 1 to 10 below. Only your answer will go beside the question number. Your page should look like the following:

11. Mental Math Susan Black 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. NOW…. Get ready to begin….

12. Question 1 48 - 27

13. Question 2 74 - 38

14. Question 3 65 - 49

15. Question 4 83 - 59

16. Question 5 25 - 17

17. Question 6 85 - 38

18. Question 7 43 - 19

19. Question 8 71 - 37

20. Question 9 94 - 38

21. Question 10 54 - 29

22. Now get ready to check your answers… 1. 21 2. 36 3. 16 4. 24 5. 8 6. 47 7. 24 8. 34 9. 56 10. 25