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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 938 · 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. 1.66 − 29 =
  2. 2.80 + 29 =
  3. 3.330 − 99 =
  4. 4.541 − 99 =
  5. 5.99 − 19 =
  6. 6.72 − 9 =
  7. 7.85 − 29 =
  8. 8.67 − 9 =
  9. 9.50 − 19 =
  10. 10.645 − 99 =
  11. 11.68 − 19 =
  12. 12.39 + 29 =
  13. 13.48 + 29 =
  14. 14.22 + 19 =
  15. 15.76 − 19 =
  16. 16.52 + 9 =
  17. 17.86 − 9 =
  18. 18.827 − 99 =
  19. 19.59 + 29 =
  20. 20.14 + 9 =
  21. 21.318 − 99 =
  22. 22.49 − 29 =
  23. 23.54 − 29 =
  24. 24.256 − 99 =
  25. 25.384 − 99 =
  26. 26.103 − 29 =
  27. 27.282 + 99 =
  28. 28.36 + 9 =
  29. 29.19 + 9 =
  30. 30.42 − 9 =
  31. 31.50 + 9 =
  32. 32.24 − 19 =
  33. 33.16 + 9 =
  34. 34.51 + 9 =
  35. 35.49 + 19 =
  36. 36.814 − 99 =
  37. 37.56 − 29 =
  38. 38.29 − 19 =
  39. 39.519 − 99 =
  40. 40.20 − 9 =

Answer key

  1. 37
  2. 109
  3. 231
  4. 442
  5. 80
  6. 63
  7. 56
  8. 58
  9. 31
  10. 546
  11. 49
  12. 68
  13. 77
  14. 41
  15. 57
  16. 61
  17. 77
  18. 728
  19. 88
  20. 23
  21. 219
  22. 20
  23. 25
  24. 157
  25. 285
  26. 74
  27. 381
  28. 45
  29. 28
  30. 33
  31. 59
  32. 5
  33. 25
  34. 60
  35. 68
  36. 715
  37. 27
  38. 10
  39. 420
  40. 11

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