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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 491 · 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. 1.73 + 29 =
  2. 2.54 − 9 =
  3. 3.57 + 19 =
  4. 4.74 − 19 =
  5. 5.303 − 99 =
  6. 6.47 + 9 =
  7. 7.35 − 9 =
  8. 8.26 + 29 =
  9. 9.739 + 99 =
  10. 10.884 − 99 =
  11. 11.288 − 99 =
  12. 12.69 + 9 =
  13. 13.34 + 29 =
  14. 14.676 − 99 =
  15. 15.246 + 99 =
  16. 16.72 − 9 =
  17. 17.82 − 19 =
  18. 18.16 + 9 =
  19. 19.54 + 19 =
  20. 20.276 − 99 =
  21. 21.58 + 9 =
  22. 22.44 − 29 =
  23. 23.62 + 29 =
  24. 24.65 + 9 =
  25. 25.51 + 9 =
  26. 26.30 − 9 =
  27. 27.43 − 29 =
  28. 28.107 + 99 =
  29. 29.800 − 99 =
  30. 30.261 − 99 =
  31. 31.90 − 19 =
  32. 32.58 − 19 =
  33. 33.304 + 99 =
  34. 34.153 − 99 =
  35. 35.61 + 9 =
  36. 36.40 + 9 =
  37. 37.424 − 99 =
  38. 38.332 + 99 =
  39. 39.23 − 9 =
  40. 40.44 − 19 =

Answer key

  1. 102
  2. 45
  3. 76
  4. 55
  5. 204
  6. 56
  7. 26
  8. 55
  9. 838
  10. 785
  11. 189
  12. 78
  13. 63
  14. 577
  15. 345
  16. 63
  17. 63
  18. 25
  19. 73
  20. 177
  21. 67
  22. 15
  23. 91
  24. 74
  25. 60
  26. 21
  27. 14
  28. 206
  29. 701
  30. 162
  31. 71
  32. 39
  33. 403
  34. 54
  35. 70
  36. 49
  37. 325
  38. 431
  39. 14
  40. 25

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