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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 337 · 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. 1.39 + 19 =
  2. 2.78 + 9 =
  3. 3.55 − 19 =
  4. 4.758 + 99 =
  5. 5.379 + 99 =
  6. 6.23 + 19 =
  7. 7.536 − 99 =
  8. 8.70 + 19 =
  9. 9.19 + 9 =
  10. 10.763 + 99 =
  11. 11.45 − 19 =
  12. 12.15 + 29 =
  13. 13.40 − 19 =
  14. 14.48 − 29 =
  15. 15.33 + 19 =
  16. 16.65 − 29 =
  17. 17.60 + 9 =
  18. 18.80 + 19 =
  19. 19.26 + 29 =
  20. 20.25 + 9 =
  21. 21.499 + 99 =
  22. 22.50 + 9 =
  23. 23.56 − 9 =
  24. 24.14 − 9 =
  25. 25.80 + 9 =
  26. 26.552 + 99 =
  27. 27.42 − 29 =
  28. 28.74 − 29 =
  29. 29.261 − 99 =
  30. 30.46 + 29 =
  31. 31.43 − 29 =
  32. 32.25 − 9 =
  33. 33.27 + 19 =
  34. 34.15 + 9 =
  35. 35.265 + 99 =
  36. 36.720 − 99 =
  37. 37.25 + 19 =
  38. 38.58 + 29 =
  39. 39.230 − 99 =
  40. 40.50 − 19 =

Answer key

  1. 58
  2. 87
  3. 36
  4. 857
  5. 478
  6. 42
  7. 437
  8. 89
  9. 28
  10. 862
  11. 26
  12. 44
  13. 21
  14. 19
  15. 52
  16. 36
  17. 69
  18. 99
  19. 55
  20. 34
  21. 598
  22. 59
  23. 47
  24. 5
  25. 89
  26. 651
  27. 13
  28. 45
  29. 162
  30. 75
  31. 14
  32. 16
  33. 46
  34. 24
  35. 364
  36. 621
  37. 44
  38. 87
  39. 131
  40. 31

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