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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 528 · 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. 1.75 + 9 =
  2. 2.321 + 99 =
  3. 3.58 + 19 =
  4. 4.50 + 9 =
  5. 5.25 − 19 =
  6. 6.145 + 99 =
  7. 7.186 + 99 =
  8. 8.20 + 9 =
  9. 9.43 − 9 =
  10. 10.42 − 29 =
  11. 11.534 + 99 =
  12. 12.12 + 19 =
  13. 13.868 − 99 =
  14. 14.72 + 19 =
  15. 15.485 − 99 =
  16. 16.51 + 19 =
  17. 17.17 − 9 =
  18. 18.12 + 9 =
  19. 19.23 + 29 =
  20. 20.527 − 99 =
  21. 21.390 + 99 =
  22. 22.53 − 19 =
  23. 23.77 − 9 =
  24. 24.253 − 99 =
  25. 25.57 + 9 =
  26. 26.460 + 99 =
  27. 27.513 + 99 =
  28. 28.49 + 19 =
  29. 29.62 + 19 =
  30. 30.24 − 19 =
  31. 31.79 + 29 =
  32. 32.28 + 29 =
  33. 33.45 − 9 =
  34. 34.67 + 9 =
  35. 35.338 + 99 =
  36. 36.51 − 19 =
  37. 37.65 + 9 =
  38. 38.49 − 9 =
  39. 39.296 + 99 =
  40. 40.399 − 99 =

Answer key

  1. 84
  2. 420
  3. 77
  4. 59
  5. 6
  6. 244
  7. 285
  8. 29
  9. 34
  10. 13
  11. 633
  12. 31
  13. 769
  14. 91
  15. 386
  16. 70
  17. 8
  18. 21
  19. 52
  20. 428
  21. 489
  22. 34
  23. 68
  24. 154
  25. 66
  26. 559
  27. 612
  28. 68
  29. 81
  30. 5
  31. 108
  32. 57
  33. 36
  34. 76
  35. 437
  36. 32
  37. 74
  38. 40
  39. 395
  40. 300

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