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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 385 · 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. 1.76 + 19 =
  2. 2.18 + 29 =
  3. 3.208 + 99 =
  4. 4.30 + 29 =
  5. 5.507 − 99 =
  6. 6.21 + 19 =
  7. 7.23 + 9 =
  8. 8.34 + 9 =
  9. 9.58 − 29 =
  10. 10.420 + 99 =
  11. 11.351 − 99 =
  12. 12.359 − 99 =
  13. 13.24 − 9 =
  14. 14.32 − 9 =
  15. 15.71 + 19 =
  16. 16.32 + 19 =
  17. 17.861 − 99 =
  18. 18.30 + 9 =
  19. 19.52 + 9 =
  20. 20.286 − 99 =
  21. 21.51 + 19 =
  22. 22.26 − 19 =
  23. 23.283 − 99 =
  24. 24.12 + 9 =
  25. 25.811 − 99 =
  26. 26.534 − 99 =
  27. 27.13 + 29 =
  28. 28.60 − 29 =
  29. 29.97 − 19 =
  30. 30.102 − 29 =
  31. 31.80 − 29 =
  32. 32.33 − 9 =
  33. 33.67 + 9 =
  34. 34.34 − 9 =
  35. 35.36 − 29 =
  36. 36.15 + 29 =
  37. 37.359 + 99 =
  38. 38.64 − 9 =
  39. 39.49 − 29 =
  40. 40.337 − 99 =

Answer key

  1. 95
  2. 47
  3. 307
  4. 59
  5. 408
  6. 40
  7. 32
  8. 43
  9. 29
  10. 519
  11. 252
  12. 260
  13. 15
  14. 23
  15. 90
  16. 51
  17. 762
  18. 39
  19. 61
  20. 187
  21. 70
  22. 7
  23. 184
  24. 21
  25. 712
  26. 435
  27. 42
  28. 31
  29. 78
  30. 73
  31. 51
  32. 24
  33. 76
  34. 25
  35. 7
  36. 44
  37. 458
  38. 55
  39. 20
  40. 238

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