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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 842 · 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. 1.82 − 9 =
  2. 2.70 − 19 =
  3. 3.15 + 9 =
  4. 4.55 − 19 =
  5. 5.76 − 19 =
  6. 6.120 + 99 =
  7. 7.194 + 99 =
  8. 8.47 + 19 =
  9. 9.602 + 99 =
  10. 10.35 + 29 =
  11. 11.78 + 9 =
  12. 12.24 − 9 =
  13. 13.288 − 99 =
  14. 14.50 + 29 =
  15. 15.22 − 19 =
  16. 16.33 − 29 =
  17. 17.648 − 99 =
  18. 18.26 + 9 =
  19. 19.280 − 99 =
  20. 20.90 − 29 =
  21. 21.50 − 19 =
  22. 22.21 + 19 =
  23. 23.73 − 9 =
  24. 24.55 − 9 =
  25. 25.16 − 9 =
  26. 26.536 + 99 =
  27. 27.598 + 99 =
  28. 28.711 + 99 =
  29. 29.40 + 29 =
  30. 30.37 − 19 =
  31. 31.19 + 9 =
  32. 32.722 − 99 =
  33. 33.60 − 29 =
  34. 34.560 − 99 =
  35. 35.48 + 19 =
  36. 36.43 + 9 =
  37. 37.45 − 19 =
  38. 38.62 − 9 =
  39. 39.62 − 29 =
  40. 40.14 + 29 =

Answer key

  1. 73
  2. 51
  3. 24
  4. 36
  5. 57
  6. 219
  7. 293
  8. 66
  9. 701
  10. 64
  11. 87
  12. 15
  13. 189
  14. 79
  15. 3
  16. 4
  17. 549
  18. 35
  19. 181
  20. 61
  21. 31
  22. 40
  23. 64
  24. 46
  25. 7
  26. 635
  27. 697
  28. 810
  29. 69
  30. 18
  31. 28
  32. 623
  33. 31
  34. 461
  35. 67
  36. 52
  37. 26
  38. 53
  39. 33
  40. 43

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