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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 458 · 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. 1.50 + 29 =
  2. 2.16 + 29 =
  3. 3.738 + 99 =
  4. 4.31 − 9 =
  5. 5.662 + 99 =
  6. 6.34 − 19 =
  7. 7.55 + 29 =
  8. 8.53 + 9 =
  9. 9.73 + 29 =
  10. 10.39 − 19 =
  11. 11.67 − 9 =
  12. 12.609 − 99 =
  13. 13.528 + 99 =
  14. 14.69 + 9 =
  15. 15.19 + 19 =
  16. 16.36 − 19 =
  17. 17.76 + 19 =
  18. 18.80 + 9 =
  19. 19.50 + 19 =
  20. 20.27 + 9 =
  21. 21.88 − 9 =
  22. 22.392 + 99 =
  23. 23.413 − 99 =
  24. 24.45 + 19 =
  25. 25.424 − 99 =
  26. 26.38 + 9 =
  27. 27.36 + 9 =
  28. 28.43 − 9 =
  29. 29.326 + 99 =
  30. 30.36 − 29 =
  31. 31.573 + 99 =
  32. 32.78 − 9 =
  33. 33.31 + 29 =
  34. 34.64 + 29 =
  35. 35.630 − 99 =
  36. 36.119 + 99 =
  37. 37.29 + 29 =
  38. 38.753 + 99 =
  39. 39.34 − 9 =
  40. 40.29 − 19 =

Answer key

  1. 79
  2. 45
  3. 837
  4. 22
  5. 761
  6. 15
  7. 84
  8. 62
  9. 102
  10. 20
  11. 58
  12. 510
  13. 627
  14. 78
  15. 38
  16. 17
  17. 95
  18. 89
  19. 69
  20. 36
  21. 79
  22. 491
  23. 314
  24. 64
  25. 325
  26. 47
  27. 45
  28. 34
  29. 425
  30. 7
  31. 672
  32. 69
  33. 60
  34. 93
  35. 531
  36. 218
  37. 58
  38. 852
  39. 25
  40. 10

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