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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 43 · 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. 1.19 + 29 =
  2. 2.57 − 9 =
  3. 3.64 − 29 =
  4. 4.25 + 9 =
  5. 5.148 + 99 =
  6. 6.65 + 9 =
  7. 7.83 − 9 =
  8. 8.49 − 29 =
  9. 9.241 − 99 =
  10. 10.69 − 29 =
  11. 11.45 + 29 =
  12. 12.38 + 9 =
  13. 13.341 + 99 =
  14. 14.41 − 9 =
  15. 15.20 + 29 =
  16. 16.136 + 99 =
  17. 17.19 + 19 =
  18. 18.64 − 19 =
  19. 19.62 + 29 =
  20. 20.605 + 99 =
  21. 21.45 − 19 =
  22. 22.27 + 19 =
  23. 23.66 + 19 =
  24. 24.75 − 9 =
  25. 25.34 − 9 =
  26. 26.19 + 9 =
  27. 27.129 + 99 =
  28. 28.36 + 9 =
  29. 29.29 + 19 =
  30. 30.164 + 99 =
  31. 31.37 + 9 =
  32. 32.287 − 99 =
  33. 33.22 − 9 =
  34. 34.30 − 19 =
  35. 35.54 + 9 =
  36. 36.59 + 29 =
  37. 37.46 + 9 =
  38. 38.623 + 99 =
  39. 39.611 − 99 =
  40. 40.46 − 19 =

Answer key

  1. 48
  2. 48
  3. 35
  4. 34
  5. 247
  6. 74
  7. 74
  8. 20
  9. 142
  10. 40
  11. 74
  12. 47
  13. 440
  14. 32
  15. 49
  16. 235
  17. 38
  18. 45
  19. 91
  20. 704
  21. 26
  22. 46
  23. 85
  24. 66
  25. 25
  26. 28
  27. 228
  28. 45
  29. 48
  30. 263
  31. 46
  32. 188
  33. 13
  34. 11
  35. 63
  36. 88
  37. 55
  38. 722
  39. 512
  40. 27

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