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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 200 · 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. 1.34 − 29 =
  2. 2.18 + 9 =
  3. 3.70 + 29 =
  4. 4.91 − 19 =
  5. 5.73 + 29 =
  6. 6.72 − 29 =
  7. 7.26 + 19 =
  8. 8.93 − 19 =
  9. 9.76 + 9 =
  10. 10.52 + 9 =
  11. 11.419 − 99 =
  12. 12.88 − 9 =
  13. 13.61 − 9 =
  14. 14.495 + 99 =
  15. 15.17 − 9 =
  16. 16.398 − 99 =
  17. 17.92 − 29 =
  18. 18.628 + 99 =
  19. 19.23 + 19 =
  20. 20.448 − 99 =
  21. 21.362 + 99 =
  22. 22.638 + 99 =
  23. 23.837 − 99 =
  24. 24.30 + 19 =
  25. 25.452 − 99 =
  26. 26.29 − 19 =
  27. 27.19 + 9 =
  28. 28.61 + 29 =
  29. 29.39 − 29 =
  30. 30.46 − 9 =
  31. 31.44 − 29 =
  32. 32.22 + 19 =
  33. 33.409 − 99 =
  34. 34.62 + 19 =
  35. 35.24 − 19 =
  36. 36.67 − 9 =
  37. 37.67 − 19 =
  38. 38.150 + 99 =
  39. 39.42 + 9 =
  40. 40.239 − 99 =

Answer key

  1. 5
  2. 27
  3. 99
  4. 72
  5. 102
  6. 43
  7. 45
  8. 74
  9. 85
  10. 61
  11. 320
  12. 79
  13. 52
  14. 594
  15. 8
  16. 299
  17. 63
  18. 727
  19. 42
  20. 349
  21. 461
  22. 737
  23. 738
  24. 49
  25. 353
  26. 10
  27. 28
  28. 90
  29. 10
  30. 37
  31. 15
  32. 41
  33. 310
  34. 81
  35. 5
  36. 58
  37. 48
  38. 249
  39. 51
  40. 140

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