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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 333 · 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. 1.70 + 19 =
  2. 2.48 − 29 =
  3. 3.72 + 29 =
  4. 4.32 + 29 =
  5. 5.35 − 9 =
  6. 6.58 − 9 =
  7. 7.636 + 99 =
  8. 8.63 − 9 =
  9. 9.16 + 19 =
  10. 10.704 − 99 =
  11. 11.15 − 9 =
  12. 12.31 + 19 =
  13. 13.25 − 19 =
  14. 14.62 − 9 =
  15. 15.90 − 19 =
  16. 16.304 − 99 =
  17. 17.234 − 99 =
  18. 18.40 + 19 =
  19. 19.41 − 29 =
  20. 20.43 + 19 =
  21. 21.15 + 9 =
  22. 22.156 + 99 =
  23. 23.356 − 99 =
  24. 24.38 + 9 =
  25. 25.39 − 29 =
  26. 26.14 + 9 =
  27. 27.35 + 29 =
  28. 28.36 − 9 =
  29. 29.84 − 19 =
  30. 30.60 − 9 =
  31. 31.885 − 99 =
  32. 32.29 + 9 =
  33. 33.80 − 29 =
  34. 34.348 − 99 =
  35. 35.56 − 29 =
  36. 36.19 + 19 =
  37. 37.261 − 99 =
  38. 38.354 + 99 =
  39. 39.46 + 19 =
  40. 40.22 − 9 =

Answer key

  1. 89
  2. 19
  3. 101
  4. 61
  5. 26
  6. 49
  7. 735
  8. 54
  9. 35
  10. 605
  11. 6
  12. 50
  13. 6
  14. 53
  15. 71
  16. 205
  17. 135
  18. 59
  19. 12
  20. 62
  21. 24
  22. 255
  23. 257
  24. 47
  25. 10
  26. 23
  27. 64
  28. 27
  29. 65
  30. 51
  31. 786
  32. 38
  33. 51
  34. 249
  35. 27
  36. 38
  37. 162
  38. 453
  39. 65
  40. 13

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