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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 328 · 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. 1.541 + 99 =
  2. 2.62 + 29 =
  3. 3.87 − 19 =
  4. 4.495 − 99 =
  5. 5.96 − 29 =
  6. 6.515 − 99 =
  7. 7.20 + 19 =
  8. 8.30 + 29 =
  9. 9.71 + 19 =
  10. 10.57 − 29 =
  11. 11.74 + 9 =
  12. 12.66 + 9 =
  13. 13.823 − 99 =
  14. 14.76 − 9 =
  15. 15.64 − 19 =
  16. 16.35 + 9 =
  17. 17.68 − 9 =
  18. 18.49 + 29 =
  19. 19.768 + 99 =
  20. 20.214 − 99 =
  21. 21.407 − 99 =
  22. 22.56 − 29 =
  23. 23.30 + 19 =
  24. 24.322 − 99 =
  25. 25.34 + 9 =
  26. 26.62 − 29 =
  27. 27.23 − 9 =
  28. 28.29 + 9 =
  29. 29.19 + 29 =
  30. 30.23 − 19 =
  31. 31.12 + 9 =
  32. 32.45 + 29 =
  33. 33.764 + 99 =
  34. 34.30 − 9 =
  35. 35.140 + 99 =
  36. 36.74 + 29 =
  37. 37.16 − 9 =
  38. 38.82 − 19 =
  39. 39.188 + 99 =
  40. 40.53 − 9 =

Answer key

  1. 640
  2. 91
  3. 68
  4. 396
  5. 67
  6. 416
  7. 39
  8. 59
  9. 90
  10. 28
  11. 83
  12. 75
  13. 724
  14. 67
  15. 45
  16. 44
  17. 59
  18. 78
  19. 867
  20. 115
  21. 308
  22. 27
  23. 49
  24. 223
  25. 43
  26. 33
  27. 14
  28. 38
  29. 48
  30. 4
  31. 21
  32. 74
  33. 863
  34. 21
  35. 239
  36. 103
  37. 7
  38. 63
  39. 287
  40. 44

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