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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 398 · 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. 1.78 + 19 =
  2. 2.424 + 99 =
  3. 3.14 + 9 =
  4. 4.70 − 19 =
  5. 5.34 − 19 =
  6. 6.87 − 9 =
  7. 7.50 + 9 =
  8. 8.12 − 9 =
  9. 9.24 + 9 =
  10. 10.43 + 9 =
  11. 11.12 + 19 =
  12. 12.85 − 29 =
  13. 13.778 − 99 =
  14. 14.55 − 9 =
  15. 15.835 − 99 =
  16. 16.44 − 19 =
  17. 17.35 + 19 =
  18. 18.58 + 9 =
  19. 19.838 − 99 =
  20. 20.72 + 29 =
  21. 21.573 + 99 =
  22. 22.38 − 29 =
  23. 23.39 − 19 =
  24. 24.17 − 9 =
  25. 25.14 + 19 =
  26. 26.686 − 99 =
  27. 27.33 − 29 =
  28. 28.67 − 29 =
  29. 29.63 + 29 =
  30. 30.74 − 19 =
  31. 31.61 − 9 =
  32. 32.448 + 99 =
  33. 33.61 − 19 =
  34. 34.33 − 19 =
  35. 35.885 − 99 =
  36. 36.45 + 29 =
  37. 37.467 + 99 =
  38. 38.85 − 9 =
  39. 39.38 − 19 =
  40. 40.45 − 29 =

Answer key

  1. 97
  2. 523
  3. 23
  4. 51
  5. 15
  6. 78
  7. 59
  8. 3
  9. 33
  10. 52
  11. 31
  12. 56
  13. 679
  14. 46
  15. 736
  16. 25
  17. 54
  18. 67
  19. 739
  20. 101
  21. 672
  22. 9
  23. 20
  24. 8
  25. 33
  26. 587
  27. 4
  28. 38
  29. 92
  30. 55
  31. 52
  32. 547
  33. 42
  34. 14
  35. 786
  36. 74
  37. 566
  38. 76
  39. 19
  40. 16

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