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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 911 · 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. 1.68 + 19 =
  2. 2.38 + 19 =
  3. 3.30 + 9 =
  4. 4.57 − 19 =
  5. 5.709 − 99 =
  6. 6.76 + 9 =
  7. 7.17 + 9 =
  8. 8.43 + 29 =
  9. 9.71 − 29 =
  10. 10.38 − 19 =
  11. 11.14 + 29 =
  12. 12.59 + 29 =
  13. 13.47 + 19 =
  14. 14.37 + 29 =
  15. 15.52 − 29 =
  16. 16.32 + 19 =
  17. 17.531 + 99 =
  18. 18.219 − 99 =
  19. 19.79 + 19 =
  20. 20.63 + 29 =
  21. 21.30 − 9 =
  22. 22.75 − 9 =
  23. 23.789 − 99 =
  24. 24.51 + 19 =
  25. 25.52 + 9 =
  26. 26.26 − 19 =
  27. 27.286 + 99 =
  28. 28.57 − 9 =
  29. 29.252 − 99 =
  30. 30.40 − 29 =
  31. 31.79 + 9 =
  32. 32.47 − 19 =
  33. 33.12 + 19 =
  34. 34.752 − 99 =
  35. 35.796 + 99 =
  36. 36.271 + 99 =
  37. 37.100 − 29 =
  38. 38.45 + 29 =
  39. 39.96 − 29 =
  40. 40.476 + 99 =

Answer key

  1. 87
  2. 57
  3. 39
  4. 38
  5. 610
  6. 85
  7. 26
  8. 72
  9. 42
  10. 19
  11. 43
  12. 88
  13. 66
  14. 66
  15. 23
  16. 51
  17. 630
  18. 120
  19. 98
  20. 92
  21. 21
  22. 66
  23. 690
  24. 70
  25. 61
  26. 7
  27. 385
  28. 48
  29. 153
  30. 11
  31. 88
  32. 28
  33. 31
  34. 653
  35. 895
  36. 370
  37. 71
  38. 74
  39. 67
  40. 575

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