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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 784 · 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. 1.23 + 29 =
  2. 2.27 − 19 =
  3. 3.27 + 19 =
  4. 4.38 − 29 =
  5. 5.779 − 99 =
  6. 6.744 + 99 =
  7. 7.32 − 29 =
  8. 8.12 + 9 =
  9. 9.20 − 9 =
  10. 10.42 − 29 =
  11. 11.53 + 29 =
  12. 12.45 + 29 =
  13. 13.668 − 99 =
  14. 14.32 − 19 =
  15. 15.69 − 29 =
  16. 16.459 + 99 =
  17. 17.70 + 19 =
  18. 18.97 − 29 =
  19. 19.16 − 9 =
  20. 20.278 + 99 =
  21. 21.29 + 29 =
  22. 22.531 + 99 =
  23. 23.402 − 99 =
  24. 24.210 + 99 =
  25. 25.17 − 9 =
  26. 26.56 + 19 =
  27. 27.674 + 99 =
  28. 28.305 + 99 =
  29. 29.58 − 19 =
  30. 30.13 + 9 =
  31. 31.14 − 9 =
  32. 32.31 − 19 =
  33. 33.21 − 9 =
  34. 34.73 + 9 =
  35. 35.15 + 9 =
  36. 36.33 − 19 =
  37. 37.44 − 9 =
  38. 38.80 + 19 =
  39. 39.593 + 99 =
  40. 40.140 + 99 =

Answer key

  1. 52
  2. 8
  3. 46
  4. 9
  5. 680
  6. 843
  7. 3
  8. 21
  9. 11
  10. 13
  11. 82
  12. 74
  13. 569
  14. 13
  15. 40
  16. 558
  17. 89
  18. 68
  19. 7
  20. 377
  21. 58
  22. 630
  23. 303
  24. 309
  25. 8
  26. 75
  27. 773
  28. 404
  29. 39
  30. 22
  31. 5
  32. 12
  33. 12
  34. 82
  35. 24
  36. 14
  37. 35
  38. 99
  39. 692
  40. 239

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