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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 930 · 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. 1.60 + 29 =
  2. 2.17 + 19 =
  3. 3.93 − 29 =
  4. 4.198 + 99 =
  5. 5.339 + 99 =
  6. 6.374 − 99 =
  7. 7.369 + 99 =
  8. 8.52 − 9 =
  9. 9.43 + 9 =
  10. 10.498 + 99 =
  11. 11.723 − 99 =
  12. 12.333 − 99 =
  13. 13.322 − 99 =
  14. 14.396 + 99 =
  15. 15.69 + 9 =
  16. 16.29 + 29 =
  17. 17.324 + 99 =
  18. 18.572 − 99 =
  19. 19.718 + 99 =
  20. 20.87 − 19 =
  21. 21.62 − 29 =
  22. 22.16 − 9 =
  23. 23.55 − 29 =
  24. 24.44 − 29 =
  25. 25.64 + 9 =
  26. 26.597 + 99 =
  27. 27.20 + 29 =
  28. 28.221 + 99 =
  29. 29.44 + 19 =
  30. 30.817 − 99 =
  31. 31.48 − 29 =
  32. 32.658 + 99 =
  33. 33.72 − 9 =
  34. 34.12 + 9 =
  35. 35.51 − 9 =
  36. 36.24 − 9 =
  37. 37.14 + 19 =
  38. 38.766 + 99 =
  39. 39.328 + 99 =
  40. 40.715 − 99 =

Answer key

  1. 89
  2. 36
  3. 64
  4. 297
  5. 438
  6. 275
  7. 468
  8. 43
  9. 52
  10. 597
  11. 624
  12. 234
  13. 223
  14. 495
  15. 78
  16. 58
  17. 423
  18. 473
  19. 817
  20. 68
  21. 33
  22. 7
  23. 26
  24. 15
  25. 73
  26. 696
  27. 49
  28. 320
  29. 63
  30. 718
  31. 19
  32. 757
  33. 63
  34. 21
  35. 42
  36. 15
  37. 33
  38. 865
  39. 427
  40. 616

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