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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 16 · 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. 1.51 + 9 =
  2. 2.26 − 9 =
  3. 3.853 − 99 =
  4. 4.26 + 9 =
  5. 5.278 + 99 =
  6. 6.36 − 29 =
  7. 7.53 − 9 =
  8. 8.75 − 29 =
  9. 9.39 − 29 =
  10. 10.842 − 99 =
  11. 11.693 + 99 =
  12. 12.23 + 9 =
  13. 13.82 − 19 =
  14. 14.29 − 19 =
  15. 15.96 − 19 =
  16. 16.62 + 9 =
  17. 17.48 + 29 =
  18. 18.29 + 29 =
  19. 19.66 + 19 =
  20. 20.12 − 9 =
  21. 21.79 + 19 =
  22. 22.651 − 99 =
  23. 23.76 − 29 =
  24. 24.32 + 19 =
  25. 25.21 + 19 =
  26. 26.53 − 29 =
  27. 27.55 + 29 =
  28. 28.52 + 9 =
  29. 29.541 − 99 =
  30. 30.144 + 99 =
  31. 31.48 + 19 =
  32. 32.94 − 19 =
  33. 33.45 + 29 =
  34. 34.14 + 19 =
  35. 35.14 + 29 =
  36. 36.47 + 29 =
  37. 37.635 − 99 =
  38. 38.252 + 99 =
  39. 39.52 + 19 =
  40. 40.163 + 99 =

Answer key

  1. 60
  2. 17
  3. 754
  4. 35
  5. 377
  6. 7
  7. 44
  8. 46
  9. 10
  10. 743
  11. 792
  12. 32
  13. 63
  14. 10
  15. 77
  16. 71
  17. 77
  18. 58
  19. 85
  20. 3
  21. 98
  22. 552
  23. 47
  24. 51
  25. 40
  26. 24
  27. 84
  28. 61
  29. 442
  30. 243
  31. 67
  32. 75
  33. 74
  34. 33
  35. 43
  36. 76
  37. 536
  38. 351
  39. 71
  40. 262

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