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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 750 · 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. 1.80 + 29 =
  2. 2.32 − 19 =
  3. 3.43 − 9 =
  4. 4.74 − 29 =
  5. 5.12 + 29 =
  6. 6.166 + 99 =
  7. 7.82 − 9 =
  8. 8.719 − 99 =
  9. 9.562 − 99 =
  10. 10.18 − 9 =
  11. 11.306 + 99 =
  12. 12.427 − 99 =
  13. 13.72 + 19 =
  14. 14.75 + 29 =
  15. 15.50 − 29 =
  16. 16.109 − 29 =
  17. 17.56 + 29 =
  18. 18.15 + 9 =
  19. 19.273 + 99 =
  20. 20.52 + 29 =
  21. 21.70 + 29 =
  22. 22.549 + 99 =
  23. 23.68 − 9 =
  24. 24.183 + 99 =
  25. 25.88 − 29 =
  26. 26.51 − 19 =
  27. 27.42 − 9 =
  28. 28.48 − 19 =
  29. 29.70 + 19 =
  30. 30.60 − 19 =
  31. 31.752 − 99 =
  32. 32.12 + 9 =
  33. 33.87 − 19 =
  34. 34.53 − 29 =
  35. 35.70 − 19 =
  36. 36.52 − 9 =
  37. 37.19 + 29 =
  38. 38.16 − 9 =
  39. 39.67 − 9 =
  40. 40.76 − 29 =

Answer key

  1. 109
  2. 13
  3. 34
  4. 45
  5. 41
  6. 265
  7. 73
  8. 620
  9. 463
  10. 9
  11. 405
  12. 328
  13. 91
  14. 104
  15. 21
  16. 80
  17. 85
  18. 24
  19. 372
  20. 81
  21. 99
  22. 648
  23. 59
  24. 282
  25. 59
  26. 32
  27. 33
  28. 29
  29. 89
  30. 41
  31. 653
  32. 21
  33. 68
  34. 24
  35. 51
  36. 43
  37. 48
  38. 7
  39. 58
  40. 47

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