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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 853 · 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. 1.630 + 99 =
  2. 2.77 + 9 =
  3. 3.22 − 19 =
  4. 4.34 − 29 =
  5. 5.70 + 9 =
  6. 6.28 − 9 =
  7. 7.672 − 99 =
  8. 8.103 − 29 =
  9. 9.865 − 99 =
  10. 10.20 − 9 =
  11. 11.35 − 29 =
  12. 12.73 − 29 =
  13. 13.79 + 19 =
  14. 14.565 + 99 =
  15. 15.47 − 29 =
  16. 16.37 − 9 =
  17. 17.14 + 19 =
  18. 18.501 − 99 =
  19. 19.15 + 9 =
  20. 20.107 − 29 =
  21. 21.87 − 9 =
  22. 22.117 + 99 =
  23. 23.288 − 99 =
  24. 24.29 − 19 =
  25. 25.70 − 19 =
  26. 26.207 + 99 =
  27. 27.84 − 29 =
  28. 28.24 + 9 =
  29. 29.877 − 99 =
  30. 30.39 + 9 =
  31. 31.18 − 9 =
  32. 32.37 − 29 =
  33. 33.62 − 19 =
  34. 34.377 + 99 =
  35. 35.52 + 29 =
  36. 36.234 + 99 =
  37. 37.14 − 9 =
  38. 38.51 + 29 =
  39. 39.16 + 9 =
  40. 40.61 + 29 =

Answer key

  1. 729
  2. 86
  3. 3
  4. 5
  5. 79
  6. 19
  7. 573
  8. 74
  9. 766
  10. 11
  11. 6
  12. 44
  13. 98
  14. 664
  15. 18
  16. 28
  17. 33
  18. 402
  19. 24
  20. 78
  21. 78
  22. 216
  23. 189
  24. 10
  25. 51
  26. 306
  27. 55
  28. 33
  29. 778
  30. 48
  31. 9
  32. 8
  33. 43
  34. 476
  35. 81
  36. 333
  37. 5
  38. 80
  39. 25
  40. 90

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