2. AddAdd 50 40 30 20 10SubtractSubtractMultiplyMultiplyDivideDivide Misc Mental Math Misc Math 170 – Chapter 3 and 4 50 40 30 20 10 50 40 30 20 10 50 40 30 20 10 FINAL 40 30 20 10

3. Addition

4. CheckWork one long-flat, two longs, three units. Go Home Go Home 10 Point Question Sketch which base 5 pieces you would need to represent 1023 5 ?

5. CheckWork Go Home Go Home Rewrite 3+(2+6) using only the commutative property of addition once. 20 Point Question 3+(6+2) or (2+6)+3

6. Use only the associative property of addition to rewrite 3+(6+2). CheckWork (3+6)+2 Go Home Go Home 30 Point Question

7. CheckWork 431 5 Go Home Go Home 40 Point Question Add the following: 233 5 +143 5

8. CheckWork Add the 237 and 23 first to get a sum of 260. Then add in the 140 to get a total of 500. Go Home Go Home Explain how to mentally compute 237 + 140 + 23 50 Point Question

9. Subtraction

10. CheckWork The take-away concept. Go Home Go Home Two models for subtraction are the comparison concept and the missing addend concept. What is the third model? 10 Point Question

11. CheckWork Go Home Go Home 20 Point Question Show, with base-5 pieces 21 5 – 14 5. Start with two longs and one unit. Since you can’t remove 4 units, trade a long for 5 units, then remove 4. Finally remove a long. You should be left with just 2 units.

12. CheckWork Go Home Go Home 30 Point Question Harry has $2500 in cash to pay for a secondhand car, or he can pay $500 down and $115 per month for 2 years. If he doesn’t pay the full amount in cash, he can invest the difference and make $150. How much money will he lose if he chooses the more expensive option? $3370 on the payment plan

13. CheckWork Go Home Go Home How can the comparison model for subtraction be used to compute 34 – 29? 40 Point Question 34 is 5 more than 29, so 34 – 29 = 5.

14. CheckWork Go Home Go Home How does the take away model for subtraction apply to the problem 43-12? 50 Point Question If you have 43 objects and someone takes away 12, you will be left with 31. So 43 – 12 = 31

15. Multiplication

16. CheckWork The identity property of multiplication Go Home Go Home Which property of multiplication is illustrated below? 1. a = a. 1 = a 10 Point Question

17. CheckWork Go Home Go Home Find the product 13 5 and 32 5 20 Point Question 1021 5

18. CheckWork 23 rows and 14 columns (or 14 rows and 23 columns.) for a total of 322 Go Home Go Home Draw an array showing 23 x 14. How many squares are enclosed? 30 Point Question

19. CheckWork 40 Go Home Go Home A store carries five styles of backpacks in four different sizes. The customer also has a choice of two different kinds of material. How many different choices does a customer have? 40 Point Question

20. CheckWork 10001 Go Home Go Home Multiplying a 4 digit number by this number is easy: just write the 4 digit number down twice in a row. What is the number? 50 Point Question

21. Division

22. CheckWork Missing factor, sharing (partitive) and measurement (subtractive.) Go Home Go Home 10 Point Question What are the three models for division?

23. CheckWork Go Home Go Home Sketch two ways to divide 48 by 8. 20 Point Question Either 6 groups of 8 (measurement) or 8 groups of 6 (sharing/partitive)

24. Use sketches of base 5 pieces to show 142 five divided by 11 five. CheckWork Start with a flat, 4 longs and 2 units. Divide them into 6 groups. There will be 1 long and 2 units in each group, with 1 long left over. (So the answer is 12 five with a remainder of 10 five. Go Home Go Home 30 Point Question

25. Go Home Go Home 40 Point Question CheckWork Evaluate 1440/12X10+18 1218

26. CheckWork Go Home Go Home 50 Point Question Find the quotient of 4052 and 8. (Using whole number division.) 506 R 4

27. Mental Math

28. CheckWork 37 and 33 Go Home Go Home Which two numbers are compatible for addition? 42, 37, 81, 55, 24, 33 10 Point Question

29. Explain how to do the following problem using mental math. 21X36 + 21X64 Use the distributative property to make it 21X(36+64) Add the compatible numbers, then multiply to get 2100. CheckWork Go Home Go Home 20 Point Question

30. CheckWork Go Home Go Home 30 Point Question Use the range method to get estimates for 236+153. Low: 300, high 500.

31. I would take 4 from the 248 and add it to the 296 so the sum becomes 244 + 300 = 544. I guess you could also take 2 from the 296 and add it to the 248 so the problem becomes 250 + 294, but my way results in an easier sum. Explain how to use the compensation method to find 248+296. CheckWork Go Home Go Home 40 Point Question

32. CheckWork Go Home Go Home Final Question Ooh. Good question. Maybe I’ll put this one on the test. In the standard multiplication algorithm, why do we “shift over one to the left” as illustrated in the 642 in the following problem? 321 X 23 963+642