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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 700 · 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. 1.71 − 19 =
  2. 2.78 − 19 =
  3. 3.19 + 9 =
  4. 4.52 + 29 =
  5. 5.44 + 9 =
  6. 6.72 − 9 =
  7. 7.220 + 99 =
  8. 8.185 − 99 =
  9. 9.24 + 9 =
  10. 10.28 + 9 =
  11. 11.18 + 19 =
  12. 12.664 + 99 =
  13. 13.655 − 99 =
  14. 14.52 − 19 =
  15. 15.45 + 29 =
  16. 16.16 − 9 =
  17. 17.50 + 9 =
  18. 18.66 + 29 =
  19. 19.77 + 29 =
  20. 20.74 + 29 =
  21. 21.28 + 29 =
  22. 22.101 − 29 =
  23. 23.35 + 19 =
  24. 24.305 − 99 =
  25. 25.42 + 9 =
  26. 26.60 + 9 =
  27. 27.78 + 19 =
  28. 28.139 + 99 =
  29. 29.48 − 19 =
  30. 30.42 + 29 =
  31. 31.63 + 9 =
  32. 32.27 + 9 =
  33. 33.552 + 99 =
  34. 34.53 + 29 =
  35. 35.117 + 99 =
  36. 36.38 − 9 =
  37. 37.25 − 19 =
  38. 38.20 + 29 =
  39. 39.29 − 19 =
  40. 40.65 − 9 =

Answer key

  1. 52
  2. 59
  3. 28
  4. 81
  5. 53
  6. 63
  7. 319
  8. 86
  9. 33
  10. 37
  11. 37
  12. 763
  13. 556
  14. 33
  15. 74
  16. 7
  17. 59
  18. 95
  19. 106
  20. 103
  21. 57
  22. 72
  23. 54
  24. 206
  25. 51
  26. 69
  27. 97
  28. 238
  29. 29
  30. 71
  31. 72
  32. 36
  33. 651
  34. 82
  35. 216
  36. 29
  37. 6
  38. 49
  39. 10
  40. 56

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