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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 766 · 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. 1.754 − 99 =
  2. 2.15 + 9 =
  3. 3.63 + 19 =
  4. 4.44 + 19 =
  5. 5.98 − 19 =
  6. 6.283 + 99 =
  7. 7.33 + 29 =
  8. 8.664 − 99 =
  9. 9.266 − 99 =
  10. 10.50 − 19 =
  11. 11.61 + 9 =
  12. 12.45 + 9 =
  13. 13.42 + 19 =
  14. 14.34 − 19 =
  15. 15.89 − 29 =
  16. 16.53 + 19 =
  17. 17.102 − 29 =
  18. 18.54 + 19 =
  19. 19.644 + 99 =
  20. 20.210 + 99 =
  21. 21.37 − 19 =
  22. 22.52 − 29 =
  23. 23.22 − 9 =
  24. 24.87 − 9 =
  25. 25.24 + 19 =
  26. 26.471 − 99 =
  27. 27.281 − 99 =
  28. 28.37 + 19 =
  29. 29.88 − 29 =
  30. 30.31 − 9 =
  31. 31.411 + 99 =
  32. 32.650 − 99 =
  33. 33.12 + 19 =
  34. 34.108 − 29 =
  35. 35.700 − 99 =
  36. 36.19 − 9 =
  37. 37.19 + 19 =
  38. 38.77 − 29 =
  39. 39.39 + 29 =
  40. 40.17 + 9 =

Answer key

  1. 655
  2. 24
  3. 82
  4. 63
  5. 79
  6. 382
  7. 62
  8. 565
  9. 167
  10. 31
  11. 70
  12. 54
  13. 61
  14. 15
  15. 60
  16. 72
  17. 73
  18. 73
  19. 743
  20. 309
  21. 18
  22. 23
  23. 13
  24. 78
  25. 43
  26. 372
  27. 182
  28. 56
  29. 59
  30. 22
  31. 510
  32. 551
  33. 31
  34. 79
  35. 601
  36. 10
  37. 38
  38. 48
  39. 68
  40. 26

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