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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 804 · 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. 1.15 + 9 =
  2. 2.28 + 9 =
  3. 3.797 + 99 =
  4. 4.69 + 19 =
  5. 5.767 − 99 =
  6. 6.12 + 19 =
  7. 7.309 − 99 =
  8. 8.43 − 9 =
  9. 9.271 + 99 =
  10. 10.68 + 9 =
  11. 11.32 + 9 =
  12. 12.30 + 9 =
  13. 13.53 + 19 =
  14. 14.37 − 19 =
  15. 15.379 + 99 =
  16. 16.274 + 99 =
  17. 17.41 − 19 =
  18. 18.40 − 19 =
  19. 19.50 − 9 =
  20. 20.42 − 19 =
  21. 21.31 + 9 =
  22. 22.53 + 9 =
  23. 23.56 − 9 =
  24. 24.18 + 9 =
  25. 25.14 + 9 =
  26. 26.56 + 19 =
  27. 27.83 − 9 =
  28. 28.80 + 19 =
  29. 29.28 + 29 =
  30. 30.623 + 99 =
  31. 31.25 − 9 =
  32. 32.63 + 9 =
  33. 33.771 − 99 =
  34. 34.541 + 99 =
  35. 35.47 − 29 =
  36. 36.69 − 29 =
  37. 37.631 + 99 =
  38. 38.44 + 19 =
  39. 39.90 − 19 =
  40. 40.21 + 19 =

Answer key

  1. 24
  2. 37
  3. 896
  4. 88
  5. 668
  6. 31
  7. 210
  8. 34
  9. 370
  10. 77
  11. 41
  12. 39
  13. 72
  14. 18
  15. 478
  16. 373
  17. 22
  18. 21
  19. 41
  20. 23
  21. 40
  22. 62
  23. 47
  24. 27
  25. 23
  26. 75
  27. 74
  28. 99
  29. 57
  30. 722
  31. 16
  32. 72
  33. 672
  34. 640
  35. 18
  36. 40
  37. 730
  38. 63
  39. 71
  40. 40

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