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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 128 · 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. 1.92 − 29 =
  2. 2.551 + 99 =
  3. 3.27 − 19 =
  4. 4.37 + 9 =
  5. 5.58 + 9 =
  6. 6.64 − 29 =
  7. 7.24 + 29 =
  8. 8.35 − 19 =
  9. 9.70 + 9 =
  10. 10.63 + 9 =
  11. 11.154 − 99 =
  12. 12.57 − 9 =
  13. 13.27 + 19 =
  14. 14.69 + 19 =
  15. 15.50 + 29 =
  16. 16.24 − 9 =
  17. 17.78 + 9 =
  18. 18.31 − 19 =
  19. 19.327 − 99 =
  20. 20.539 + 99 =
  21. 21.29 − 19 =
  22. 22.50 + 9 =
  23. 23.853 − 99 =
  24. 24.546 + 99 =
  25. 25.59 − 9 =
  26. 26.62 + 19 =
  27. 27.34 − 29 =
  28. 28.15 + 19 =
  29. 29.86 − 29 =
  30. 30.57 + 19 =
  31. 31.688 − 99 =
  32. 32.20 + 9 =
  33. 33.65 − 19 =
  34. 34.55 + 9 =
  35. 35.173 + 99 =
  36. 36.93 − 19 =
  37. 37.80 − 29 =
  38. 38.17 + 19 =
  39. 39.60 + 9 =
  40. 40.71 + 29 =

Answer key

  1. 63
  2. 650
  3. 8
  4. 46
  5. 67
  6. 35
  7. 53
  8. 16
  9. 79
  10. 72
  11. 55
  12. 48
  13. 46
  14. 88
  15. 79
  16. 15
  17. 87
  18. 12
  19. 228
  20. 638
  21. 10
  22. 59
  23. 754
  24. 645
  25. 50
  26. 81
  27. 5
  28. 34
  29. 57
  30. 76
  31. 589
  32. 29
  33. 46
  34. 64
  35. 272
  36. 74
  37. 51
  38. 36
  39. 69
  40. 100

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