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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 338 · 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. 1.59 + 9 =
  2. 2.68 + 19 =
  3. 3.581 − 99 =
  4. 4.178 − 99 =
  5. 5.14 + 19 =
  6. 6.45 + 29 =
  7. 7.203 + 99 =
  8. 8.37 + 19 =
  9. 9.59 + 19 =
  10. 10.45 − 9 =
  11. 11.14 + 29 =
  12. 12.92 − 29 =
  13. 13.389 + 99 =
  14. 14.42 + 29 =
  15. 15.53 − 19 =
  16. 16.29 − 19 =
  17. 17.70 − 9 =
  18. 18.42 − 19 =
  19. 19.494 + 99 =
  20. 20.35 − 19 =
  21. 21.159 + 99 =
  22. 22.63 − 9 =
  23. 23.80 + 29 =
  24. 24.80 + 19 =
  25. 25.40 − 29 =
  26. 26.99 − 29 =
  27. 27.42 + 19 =
  28. 28.50 + 19 =
  29. 29.82 − 29 =
  30. 30.891 − 99 =
  31. 31.74 + 29 =
  32. 32.30 − 9 =
  33. 33.18 + 29 =
  34. 34.19 + 29 =
  35. 35.715 − 99 =
  36. 36.58 + 9 =
  37. 37.22 − 19 =
  38. 38.69 + 19 =
  39. 39.427 + 99 =
  40. 40.38 + 9 =

Answer key

  1. 68
  2. 87
  3. 482
  4. 79
  5. 33
  6. 74
  7. 302
  8. 56
  9. 78
  10. 36
  11. 43
  12. 63
  13. 488
  14. 71
  15. 34
  16. 10
  17. 61
  18. 23
  19. 593
  20. 16
  21. 258
  22. 54
  23. 109
  24. 99
  25. 11
  26. 70
  27. 61
  28. 69
  29. 53
  30. 792
  31. 103
  32. 21
  33. 47
  34. 48
  35. 616
  36. 67
  37. 3
  38. 88
  39. 526
  40. 47

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