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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 218 · 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. 1.20 + 9 =
  2. 2.700 − 99 =
  3. 3.43 + 19 =
  4. 4.219 + 99 =
  5. 5.24 + 9 =
  6. 6.38 − 19 =
  7. 7.69 + 19 =
  8. 8.397 + 99 =
  9. 9.62 + 9 =
  10. 10.38 − 9 =
  11. 11.66 − 9 =
  12. 12.38 + 19 =
  13. 13.561 + 99 =
  14. 14.69 + 29 =
  15. 15.372 + 99 =
  16. 16.71 − 29 =
  17. 17.56 + 29 =
  18. 18.29 + 19 =
  19. 19.53 − 19 =
  20. 20.668 + 99 =
  21. 21.71 − 19 =
  22. 22.61 − 29 =
  23. 23.59 − 19 =
  24. 24.399 + 99 =
  25. 25.108 − 29 =
  26. 26.107 − 29 =
  27. 27.25 + 29 =
  28. 28.378 − 99 =
  29. 29.330 − 99 =
  30. 30.51 − 9 =
  31. 31.47 − 29 =
  32. 32.51 + 9 =
  33. 33.33 − 29 =
  34. 34.43 − 19 =
  35. 35.52 − 19 =
  36. 36.33 − 9 =
  37. 37.63 − 19 =
  38. 38.23 + 9 =
  39. 39.881 − 99 =
  40. 40.50 − 29 =

Answer key

  1. 29
  2. 601
  3. 62
  4. 318
  5. 33
  6. 19
  7. 88
  8. 496
  9. 71
  10. 29
  11. 57
  12. 57
  13. 660
  14. 98
  15. 471
  16. 42
  17. 85
  18. 48
  19. 34
  20. 767
  21. 52
  22. 32
  23. 40
  24. 498
  25. 79
  26. 78
  27. 54
  28. 279
  29. 231
  30. 42
  31. 18
  32. 60
  33. 4
  34. 24
  35. 33
  36. 24
  37. 44
  38. 32
  39. 782
  40. 21

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