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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 657 · 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. 1.336 + 99 =
  2. 2.38 + 9 =
  3. 3.788 + 99 =
  4. 4.61 + 19 =
  5. 5.64 + 19 =
  6. 6.92 − 29 =
  7. 7.25 + 9 =
  8. 8.42 + 9 =
  9. 9.47 + 9 =
  10. 10.406 − 99 =
  11. 11.12 − 9 =
  12. 12.54 − 29 =
  13. 13.79 + 19 =
  14. 14.35 + 19 =
  15. 15.45 − 9 =
  16. 16.335 − 99 =
  17. 17.24 − 19 =
  18. 18.57 + 29 =
  19. 19.46 + 29 =
  20. 20.43 − 9 =
  21. 21.526 − 99 =
  22. 22.42 − 9 =
  23. 23.12 + 29 =
  24. 24.78 − 19 =
  25. 25.67 + 9 =
  26. 26.22 + 19 =
  27. 27.796 − 99 =
  28. 28.133 + 99 =
  29. 29.13 + 19 =
  30. 30.44 + 29 =
  31. 31.30 + 9 =
  32. 32.14 − 9 =
  33. 33.74 − 19 =
  34. 34.28 + 19 =
  35. 35.297 + 99 =
  36. 36.15 − 9 =
  37. 37.273 − 99 =
  38. 38.25 + 29 =
  39. 39.23 + 19 =
  40. 40.99 − 29 =

Answer key

  1. 435
  2. 47
  3. 887
  4. 80
  5. 83
  6. 63
  7. 34
  8. 51
  9. 56
  10. 307
  11. 3
  12. 25
  13. 98
  14. 54
  15. 36
  16. 236
  17. 5
  18. 86
  19. 75
  20. 34
  21. 427
  22. 33
  23. 41
  24. 59
  25. 76
  26. 41
  27. 697
  28. 232
  29. 32
  30. 73
  31. 39
  32. 5
  33. 55
  34. 47
  35. 396
  36. 6
  37. 174
  38. 54
  39. 42
  40. 70

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