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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 306 · 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. 1.61 − 19 =
  2. 2.63 − 19 =
  3. 3.274 − 99 =
  4. 4.52 + 29 =
  5. 5.59 − 29 =
  6. 6.13 + 29 =
  7. 7.17 + 9 =
  8. 8.36 + 19 =
  9. 9.35 + 19 =
  10. 10.57 + 29 =
  11. 11.203 + 99 =
  12. 12.306 + 99 =
  13. 13.34 − 19 =
  14. 14.19 − 9 =
  15. 15.32 + 29 =
  16. 16.29 + 9 =
  17. 17.669 − 99 =
  18. 18.214 − 99 =
  19. 19.485 − 99 =
  20. 20.40 + 9 =
  21. 21.202 − 99 =
  22. 22.31 + 29 =
  23. 23.58 − 19 =
  24. 24.97 − 19 =
  25. 25.307 + 99 =
  26. 26.44 − 29 =
  27. 27.50 + 19 =
  28. 28.28 − 9 =
  29. 29.208 + 99 =
  30. 30.40 − 19 =
  31. 31.19 + 29 =
  32. 32.71 + 29 =
  33. 33.235 + 99 =
  34. 34.65 + 9 =
  35. 35.71 − 9 =
  36. 36.45 + 19 =
  37. 37.48 − 29 =
  38. 38.66 − 19 =
  39. 39.19 + 9 =
  40. 40.645 + 99 =

Answer key

  1. 42
  2. 44
  3. 175
  4. 81
  5. 30
  6. 42
  7. 26
  8. 55
  9. 54
  10. 86
  11. 302
  12. 405
  13. 15
  14. 10
  15. 61
  16. 38
  17. 570
  18. 115
  19. 386
  20. 49
  21. 103
  22. 60
  23. 39
  24. 78
  25. 406
  26. 15
  27. 69
  28. 19
  29. 307
  30. 21
  31. 48
  32. 100
  33. 334
  34. 74
  35. 62
  36. 64
  37. 19
  38. 47
  39. 28
  40. 744

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