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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 472 · 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. 1.66 − 9 =
  2. 2.494 + 99 =
  3. 3.528 − 99 =
  4. 4.94 − 19 =
  5. 5.65 + 9 =
  6. 6.562 + 99 =
  7. 7.57 − 9 =
  8. 8.361 − 99 =
  9. 9.30 − 9 =
  10. 10.525 − 99 =
  11. 11.81 − 29 =
  12. 12.85 − 9 =
  13. 13.383 − 99 =
  14. 14.280 − 99 =
  15. 15.227 + 99 =
  16. 16.46 + 9 =
  17. 17.98 − 19 =
  18. 18.50 + 9 =
  19. 19.303 + 99 =
  20. 20.28 + 9 =
  21. 21.17 + 9 =
  22. 22.93 − 29 =
  23. 23.52 + 9 =
  24. 24.33 + 9 =
  25. 25.182 − 99 =
  26. 26.87 − 19 =
  27. 27.107 − 29 =
  28. 28.74 − 19 =
  29. 29.60 − 29 =
  30. 30.62 + 19 =
  31. 31.109 + 99 =
  32. 32.67 + 29 =
  33. 33.68 − 29 =
  34. 34.59 + 9 =
  35. 35.61 − 19 =
  36. 36.45 + 9 =
  37. 37.217 + 99 =
  38. 38.53 − 19 =
  39. 39.400 − 99 =
  40. 40.76 − 19 =

Answer key

  1. 57
  2. 593
  3. 429
  4. 75
  5. 74
  6. 661
  7. 48
  8. 262
  9. 21
  10. 426
  11. 52
  12. 76
  13. 284
  14. 181
  15. 326
  16. 55
  17. 79
  18. 59
  19. 402
  20. 37
  21. 26
  22. 64
  23. 61
  24. 42
  25. 83
  26. 68
  27. 78
  28. 55
  29. 31
  30. 81
  31. 208
  32. 96
  33. 39
  34. 68
  35. 42
  36. 54
  37. 316
  38. 34
  39. 301
  40. 57

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