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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 632 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.280 + 99 =
  2. 2.31 − 9 =
  3. 3.57 + 29 =
  4. 4.17 − 9 =
  5. 5.16 + 29 =
  6. 6.51 − 19 =
  7. 7.661 − 99 =
  8. 8.34 − 19 =
  9. 9.51 + 19 =
  10. 10.72 + 29 =
  11. 11.37 − 19 =
  12. 12.54 − 29 =
  13. 13.30 + 9 =
  14. 14.65 + 19 =
  15. 15.634 − 99 =
  16. 16.712 − 99 =
  17. 17.16 + 19 =
  18. 18.77 + 19 =
  19. 19.45 − 9 =
  20. 20.50 − 9 =
  21. 21.417 − 99 =
  22. 22.766 + 99 =
  23. 23.513 + 99 =
  24. 24.43 − 9 =
  25. 25.58 + 29 =
  26. 26.696 + 99 =
  27. 27.22 + 9 =
  28. 28.14 + 9 =
  29. 29.70 − 29 =
  30. 30.40 + 29 =
  31. 31.217 + 99 =
  32. 32.90 − 19 =
  33. 33.63 − 29 =
  34. 34.24 + 19 =
  35. 35.415 − 99 =
  36. 36.576 + 99 =
  37. 37.19 − 9 =
  38. 38.27 + 29 =
  39. 39.176 − 99 =
  40. 40.58 + 19 =

Answer key

  1. 379
  2. 22
  3. 86
  4. 8
  5. 45
  6. 32
  7. 562
  8. 15
  9. 70
  10. 101
  11. 18
  12. 25
  13. 39
  14. 84
  15. 535
  16. 613
  17. 35
  18. 96
  19. 36
  20. 41
  21. 318
  22. 865
  23. 612
  24. 34
  25. 87
  26. 795
  27. 31
  28. 23
  29. 41
  30. 69
  31. 316
  32. 71
  33. 34
  34. 43
  35. 316
  36. 675
  37. 10
  38. 56
  39. 77
  40. 77

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