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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 238 · 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. 1.181 + 99 =
  2. 2.31 + 19 =
  3. 3.74 + 19 =
  4. 4.58 − 19 =
  5. 5.22 + 9 =
  6. 6.20 − 9 =
  7. 7.68 − 19 =
  8. 8.80 + 29 =
  9. 9.369 − 99 =
  10. 10.85 − 9 =
  11. 11.337 + 99 =
  12. 12.34 + 9 =
  13. 13.47 − 29 =
  14. 14.831 − 99 =
  15. 15.26 + 19 =
  16. 16.42 + 19 =
  17. 17.61 + 19 =
  18. 18.19 + 9 =
  19. 19.33 + 19 =
  20. 20.102 − 29 =
  21. 21.158 − 99 =
  22. 22.76 + 29 =
  23. 23.56 + 9 =
  24. 24.80 − 29 =
  25. 25.106 − 29 =
  26. 26.45 − 19 =
  27. 27.196 − 99 =
  28. 28.56 − 29 =
  29. 29.13 + 29 =
  30. 30.469 + 99 =
  31. 31.35 − 9 =
  32. 32.74 − 19 =
  33. 33.27 − 9 =
  34. 34.47 + 19 =
  35. 35.74 + 29 =
  36. 36.184 − 99 =
  37. 37.449 − 99 =
  38. 38.55 + 19 =
  39. 39.64 − 29 =
  40. 40.67 − 19 =

Answer key

  1. 280
  2. 50
  3. 93
  4. 39
  5. 31
  6. 11
  7. 49
  8. 109
  9. 270
  10. 76
  11. 436
  12. 43
  13. 18
  14. 732
  15. 45
  16. 61
  17. 80
  18. 28
  19. 52
  20. 73
  21. 59
  22. 105
  23. 65
  24. 51
  25. 77
  26. 26
  27. 97
  28. 27
  29. 42
  30. 568
  31. 26
  32. 55
  33. 18
  34. 66
  35. 103
  36. 85
  37. 350
  38. 74
  39. 35
  40. 48

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