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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 379 · 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. 1.77 − 9 =
  2. 2.68 − 9 =
  3. 3.248 + 99 =
  4. 4.43 − 29 =
  5. 5.19 + 29 =
  6. 6.74 + 29 =
  7. 7.80 + 9 =
  8. 8.43 + 29 =
  9. 9.23 + 9 =
  10. 10.101 − 29 =
  11. 11.55 − 29 =
  12. 12.56 + 19 =
  13. 13.30 + 9 =
  14. 14.16 + 9 =
  15. 15.43 + 9 =
  16. 16.35 − 9 =
  17. 17.676 + 99 =
  18. 18.51 + 29 =
  19. 19.219 + 99 =
  20. 20.20 + 19 =
  21. 21.44 + 19 =
  22. 22.32 + 9 =
  23. 23.52 + 9 =
  24. 24.340 − 99 =
  25. 25.463 − 99 =
  26. 26.568 + 99 =
  27. 27.53 + 29 =
  28. 28.226 + 99 =
  29. 29.15 − 9 =
  30. 30.499 − 99 =
  31. 31.78 + 9 =
  32. 32.45 − 9 =
  33. 33.70 + 29 =
  34. 34.179 + 99 =
  35. 35.194 − 99 =
  36. 36.52 − 29 =
  37. 37.128 + 99 =
  38. 38.81 − 9 =
  39. 39.136 + 99 =
  40. 40.46 − 9 =

Answer key

  1. 68
  2. 59
  3. 347
  4. 14
  5. 48
  6. 103
  7. 89
  8. 72
  9. 32
  10. 72
  11. 26
  12. 75
  13. 39
  14. 25
  15. 52
  16. 26
  17. 775
  18. 80
  19. 318
  20. 39
  21. 63
  22. 41
  23. 61
  24. 241
  25. 364
  26. 667
  27. 82
  28. 325
  29. 6
  30. 400
  31. 87
  32. 36
  33. 99
  34. 278
  35. 95
  36. 23
  37. 227
  38. 72
  39. 235
  40. 37

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