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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 562 · 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. 1.77 − 29 =
  2. 2.251 − 99 =
  3. 3.32 + 9 =
  4. 4.18 + 19 =
  5. 5.45 − 29 =
  6. 6.33 + 9 =
  7. 7.726 + 99 =
  8. 8.49 + 29 =
  9. 9.61 − 29 =
  10. 10.583 + 99 =
  11. 11.12 − 9 =
  12. 12.83 − 29 =
  13. 13.38 + 19 =
  14. 14.567 − 99 =
  15. 15.13 + 19 =
  16. 16.487 − 99 =
  17. 17.210 + 99 =
  18. 18.74 + 29 =
  19. 19.41 − 29 =
  20. 20.80 − 19 =
  21. 21.110 + 99 =
  22. 22.80 + 19 =
  23. 23.33 − 19 =
  24. 24.518 − 99 =
  25. 25.56 + 9 =
  26. 26.34 − 9 =
  27. 27.241 + 99 =
  28. 28.20 + 19 =
  29. 29.53 + 29 =
  30. 30.53 + 19 =
  31. 31.27 + 19 =
  32. 32.51 + 9 =
  33. 33.76 − 19 =
  34. 34.189 − 99 =
  35. 35.42 − 29 =
  36. 36.56 − 19 =
  37. 37.24 − 9 =
  38. 38.70 − 9 =
  39. 39.129 + 99 =
  40. 40.50 + 29 =

Answer key

  1. 48
  2. 152
  3. 41
  4. 37
  5. 16
  6. 42
  7. 825
  8. 78
  9. 32
  10. 682
  11. 3
  12. 54
  13. 57
  14. 468
  15. 32
  16. 388
  17. 309
  18. 103
  19. 12
  20. 61
  21. 209
  22. 99
  23. 14
  24. 419
  25. 65
  26. 25
  27. 340
  28. 39
  29. 82
  30. 72
  31. 46
  32. 60
  33. 57
  34. 90
  35. 13
  36. 37
  37. 15
  38. 61
  39. 228
  40. 79

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