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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 48 · 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. 1.68 + 9 =
  2. 2.225 + 99 =
  3. 3.43 + 9 =
  4. 4.70 + 29 =
  5. 5.52 + 29 =
  6. 6.63 − 29 =
  7. 7.72 + 19 =
  8. 8.13 + 9 =
  9. 9.74 + 9 =
  10. 10.14 + 19 =
  11. 11.52 − 19 =
  12. 12.803 − 99 =
  13. 13.69 + 29 =
  14. 14.49 − 9 =
  15. 15.45 + 9 =
  16. 16.12 − 9 =
  17. 17.76 + 29 =
  18. 18.570 + 99 =
  19. 19.60 − 29 =
  20. 20.543 − 99 =
  21. 21.39 + 9 =
  22. 22.38 + 29 =
  23. 23.64 − 9 =
  24. 24.345 + 99 =
  25. 25.52 + 19 =
  26. 26.73 + 9 =
  27. 27.184 + 99 =
  28. 28.29 + 9 =
  29. 29.430 − 99 =
  30. 30.78 − 9 =
  31. 31.46 + 9 =
  32. 32.33 − 29 =
  33. 33.88 − 19 =
  34. 34.37 − 19 =
  35. 35.12 + 9 =
  36. 36.806 − 99 =
  37. 37.34 + 9 =
  38. 38.505 + 99 =
  39. 39.516 − 99 =
  40. 40.16 − 9 =

Answer key

  1. 77
  2. 324
  3. 52
  4. 99
  5. 81
  6. 34
  7. 91
  8. 22
  9. 83
  10. 33
  11. 33
  12. 704
  13. 98
  14. 40
  15. 54
  16. 3
  17. 105
  18. 669
  19. 31
  20. 444
  21. 48
  22. 67
  23. 55
  24. 444
  25. 71
  26. 82
  27. 283
  28. 38
  29. 331
  30. 69
  31. 55
  32. 4
  33. 69
  34. 18
  35. 21
  36. 707
  37. 43
  38. 604
  39. 417
  40. 7

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