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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 59 · 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. 1.394 − 99 =
  2. 2.59 − 19 =
  3. 3.45 + 29 =
  4. 4.70 − 19 =
  5. 5.446 + 99 =
  6. 6.178 − 99 =
  7. 7.637 + 99 =
  8. 8.52 − 9 =
  9. 9.49 − 19 =
  10. 10.35 − 19 =
  11. 11.79 + 19 =
  12. 12.501 − 99 =
  13. 13.13 + 9 =
  14. 14.94 − 29 =
  15. 15.49 − 9 =
  16. 16.32 + 29 =
  17. 17.51 + 19 =
  18. 18.70 + 9 =
  19. 19.61 + 29 =
  20. 20.49 + 19 =
  21. 21.613 − 99 =
  22. 22.51 + 29 =
  23. 23.152 + 99 =
  24. 24.77 − 9 =
  25. 25.379 − 99 =
  26. 26.59 − 29 =
  27. 27.65 + 29 =
  28. 28.700 + 99 =
  29. 29.37 − 29 =
  30. 30.246 + 99 =
  31. 31.422 + 99 =
  32. 32.75 + 9 =
  33. 33.38 + 9 =
  34. 34.58 + 29 =
  35. 35.58 − 9 =
  36. 36.25 − 9 =
  37. 37.502 − 99 =
  38. 38.51 − 29 =
  39. 39.27 + 9 =
  40. 40.757 + 99 =

Answer key

  1. 295
  2. 40
  3. 74
  4. 51
  5. 545
  6. 79
  7. 736
  8. 43
  9. 30
  10. 16
  11. 98
  12. 402
  13. 22
  14. 65
  15. 40
  16. 61
  17. 70
  18. 79
  19. 90
  20. 68
  21. 514
  22. 80
  23. 251
  24. 68
  25. 280
  26. 30
  27. 94
  28. 799
  29. 8
  30. 345
  31. 521
  32. 84
  33. 47
  34. 87
  35. 49
  36. 16
  37. 403
  38. 22
  39. 36
  40. 856

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