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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 318 · 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. 1.70 + 29 =
  2. 2.32 − 19 =
  3. 3.544 − 99 =
  4. 4.38 + 9 =
  5. 5.35 − 9 =
  6. 6.416 − 99 =
  7. 7.14 + 9 =
  8. 8.476 + 99 =
  9. 9.45 − 29 =
  10. 10.16 + 19 =
  11. 11.25 − 19 =
  12. 12.64 + 9 =
  13. 13.49 + 19 =
  14. 14.38 + 19 =
  15. 15.387 + 99 =
  16. 16.31 + 9 =
  17. 17.50 − 29 =
  18. 18.51 + 19 =
  19. 19.75 + 19 =
  20. 20.72 + 9 =
  21. 21.31 − 9 =
  22. 22.517 + 99 =
  23. 23.53 − 19 =
  24. 24.776 + 99 =
  25. 25.85 − 19 =
  26. 26.67 − 29 =
  27. 27.49 − 9 =
  28. 28.275 + 99 =
  29. 29.48 + 29 =
  30. 30.42 + 9 =
  31. 31.300 − 99 =
  32. 32.813 − 99 =
  33. 33.292 − 99 =
  34. 34.42 − 19 =
  35. 35.108 − 29 =
  36. 36.51 − 19 =
  37. 37.44 − 19 =
  38. 38.579 − 99 =
  39. 39.34 + 9 =
  40. 40.28 − 9 =

Answer key

  1. 99
  2. 13
  3. 445
  4. 47
  5. 26
  6. 317
  7. 23
  8. 575
  9. 16
  10. 35
  11. 6
  12. 73
  13. 68
  14. 57
  15. 486
  16. 40
  17. 21
  18. 70
  19. 94
  20. 81
  21. 22
  22. 616
  23. 34
  24. 875
  25. 66
  26. 38
  27. 40
  28. 374
  29. 77
  30. 51
  31. 201
  32. 714
  33. 193
  34. 23
  35. 79
  36. 32
  37. 25
  38. 480
  39. 43
  40. 19

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