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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 523 · 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. 1.99 − 29 =
  2. 2.67 + 29 =
  3. 3.63 + 29 =
  4. 4.79 − 9 =
  5. 5.70 − 19 =
  6. 6.94 − 19 =
  7. 7.53 − 29 =
  8. 8.33 + 9 =
  9. 9.52 + 9 =
  10. 10.37 − 19 =
  11. 11.74 − 19 =
  12. 12.47 + 19 =
  13. 13.32 + 29 =
  14. 14.22 − 9 =
  15. 15.27 + 19 =
  16. 16.52 + 19 =
  17. 17.100 − 29 =
  18. 18.105 + 99 =
  19. 19.104 − 29 =
  20. 20.20 + 9 =
  21. 21.78 + 29 =
  22. 22.30 − 9 =
  23. 23.61 − 9 =
  24. 24.65 + 29 =
  25. 25.98 − 19 =
  26. 26.701 + 99 =
  27. 27.340 + 99 =
  28. 28.53 − 19 =
  29. 29.41 + 19 =
  30. 30.68 − 19 =
  31. 31.55 − 19 =
  32. 32.710 − 99 =
  33. 33.53 + 9 =
  34. 34.45 + 29 =
  35. 35.37 − 9 =
  36. 36.96 − 29 =
  37. 37.60 − 9 =
  38. 38.56 + 29 =
  39. 39.57 − 9 =
  40. 40.62 + 19 =

Answer key

  1. 70
  2. 96
  3. 92
  4. 70
  5. 51
  6. 75
  7. 24
  8. 42
  9. 61
  10. 18
  11. 55
  12. 66
  13. 61
  14. 13
  15. 46
  16. 71
  17. 71
  18. 204
  19. 75
  20. 29
  21. 107
  22. 21
  23. 52
  24. 94
  25. 79
  26. 800
  27. 439
  28. 34
  29. 60
  30. 49
  31. 36
  32. 611
  33. 62
  34. 74
  35. 28
  36. 67
  37. 51
  38. 85
  39. 48
  40. 81

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