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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 552 · 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. 1.74 + 29 =
  2. 2.69 − 29 =
  3. 3.77 + 19 =
  4. 4.45 − 29 =
  5. 5.552 + 99 =
  6. 6.30 − 9 =
  7. 7.47 + 29 =
  8. 8.17 + 29 =
  9. 9.29 − 19 =
  10. 10.12 − 9 =
  11. 11.51 − 9 =
  12. 12.57 + 9 =
  13. 13.295 − 99 =
  14. 14.62 + 29 =
  15. 15.207 − 99 =
  16. 16.400 + 99 =
  17. 17.24 − 19 =
  18. 18.23 + 29 =
  19. 19.59 − 19 =
  20. 20.24 + 9 =
  21. 21.81 − 19 =
  22. 22.299 − 99 =
  23. 23.14 + 29 =
  24. 24.207 + 99 =
  25. 25.50 + 19 =
  26. 26.52 + 29 =
  27. 27.61 + 29 =
  28. 28.77 − 9 =
  29. 29.51 − 19 =
  30. 30.57 − 9 =
  31. 31.31 − 9 =
  32. 32.486 + 99 =
  33. 33.33 − 9 =
  34. 34.25 − 19 =
  35. 35.25 + 29 =
  36. 36.43 − 9 =
  37. 37.22 + 9 =
  38. 38.54 + 19 =
  39. 39.43 + 9 =
  40. 40.22 + 19 =

Answer key

  1. 103
  2. 40
  3. 96
  4. 16
  5. 651
  6. 21
  7. 76
  8. 46
  9. 10
  10. 3
  11. 42
  12. 66
  13. 196
  14. 91
  15. 108
  16. 499
  17. 5
  18. 52
  19. 40
  20. 33
  21. 62
  22. 200
  23. 43
  24. 306
  25. 69
  26. 81
  27. 90
  28. 68
  29. 32
  30. 48
  31. 22
  32. 585
  33. 24
  34. 6
  35. 54
  36. 34
  37. 31
  38. 73
  39. 52
  40. 41

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