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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 706 · 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. 1.53 + 9 =
  2. 2.232 + 99 =
  3. 3.61 − 19 =
  4. 4.77 − 29 =
  5. 5.69 − 29 =
  6. 6.431 + 99 =
  7. 7.291 + 99 =
  8. 8.684 + 99 =
  9. 9.238 + 99 =
  10. 10.74 + 9 =
  11. 11.19 + 29 =
  12. 12.628 + 99 =
  13. 13.76 − 9 =
  14. 14.62 + 29 =
  15. 15.298 + 99 =
  16. 16.23 + 9 =
  17. 17.140 + 99 =
  18. 18.80 − 19 =
  19. 19.79 + 9 =
  20. 20.82 − 9 =
  21. 21.14 − 9 =
  22. 22.56 + 9 =
  23. 23.386 + 99 =
  24. 24.435 + 99 =
  25. 25.124 + 99 =
  26. 26.43 + 29 =
  27. 27.57 − 9 =
  28. 28.75 + 9 =
  29. 29.73 + 9 =
  30. 30.90 − 29 =
  31. 31.29 + 19 =
  32. 32.214 − 99 =
  33. 33.51 − 9 =
  34. 34.55 + 19 =
  35. 35.35 + 19 =
  36. 36.211 + 99 =
  37. 37.58 + 19 =
  38. 38.17 + 9 =
  39. 39.160 + 99 =
  40. 40.17 + 19 =

Answer key

  1. 62
  2. 331
  3. 42
  4. 48
  5. 40
  6. 530
  7. 390
  8. 783
  9. 337
  10. 83
  11. 48
  12. 727
  13. 67
  14. 91
  15. 397
  16. 32
  17. 239
  18. 61
  19. 88
  20. 73
  21. 5
  22. 65
  23. 485
  24. 534
  25. 223
  26. 72
  27. 48
  28. 84
  29. 82
  30. 61
  31. 48
  32. 115
  33. 42
  34. 74
  35. 54
  36. 310
  37. 77
  38. 26
  39. 259
  40. 36

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