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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 205 · 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. 1.295 − 99 =
  2. 2.56 − 19 =
  3. 3.29 + 9 =
  4. 4.90 − 19 =
  5. 5.371 + 99 =
  6. 6.68 + 19 =
  7. 7.65 + 19 =
  8. 8.84 − 9 =
  9. 9.76 − 29 =
  10. 10.13 + 9 =
  11. 11.58 − 29 =
  12. 12.238 + 99 =
  13. 13.327 − 99 =
  14. 14.758 + 99 =
  15. 15.70 − 29 =
  16. 16.30 + 19 =
  17. 17.72 + 9 =
  18. 18.99 − 19 =
  19. 19.445 − 99 =
  20. 20.45 + 19 =
  21. 21.210 + 99 =
  22. 22.36 − 9 =
  23. 23.76 + 29 =
  24. 24.79 + 19 =
  25. 25.642 − 99 =
  26. 26.108 + 99 =
  27. 27.25 − 9 =
  28. 28.35 − 29 =
  29. 29.61 − 9 =
  30. 30.29 + 19 =
  31. 31.67 − 29 =
  32. 32.65 + 9 =
  33. 33.52 + 9 =
  34. 34.65 − 19 =
  35. 35.64 + 29 =
  36. 36.473 + 99 =
  37. 37.101 − 29 =
  38. 38.70 + 19 =
  39. 39.24 + 9 =
  40. 40.72 + 19 =

Answer key

  1. 196
  2. 37
  3. 38
  4. 71
  5. 470
  6. 87
  7. 84
  8. 75
  9. 47
  10. 22
  11. 29
  12. 337
  13. 228
  14. 857
  15. 41
  16. 49
  17. 81
  18. 80
  19. 346
  20. 64
  21. 309
  22. 27
  23. 105
  24. 98
  25. 543
  26. 207
  27. 16
  28. 6
  29. 52
  30. 48
  31. 38
  32. 74
  33. 61
  34. 46
  35. 93
  36. 572
  37. 72
  38. 89
  39. 33
  40. 91

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