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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 698 · 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. 1.64 + 9 =
  2. 2.616 + 99 =
  3. 3.593 + 99 =
  4. 4.131 + 99 =
  5. 5.16 + 19 =
  6. 6.63 + 29 =
  7. 7.292 + 99 =
  8. 8.53 − 9 =
  9. 9.645 − 99 =
  10. 10.98 − 29 =
  11. 11.572 + 99 =
  12. 12.124 + 99 =
  13. 13.378 + 99 =
  14. 14.73 − 9 =
  15. 15.807 − 99 =
  16. 16.69 + 19 =
  17. 17.57 + 19 =
  18. 18.73 + 9 =
  19. 19.410 + 99 =
  20. 20.69 − 19 =
  21. 21.413 + 99 =
  22. 22.61 − 19 =
  23. 23.299 − 99 =
  24. 24.80 + 9 =
  25. 25.45 − 9 =
  26. 26.30 + 9 =
  27. 27.352 − 99 =
  28. 28.594 + 99 =
  29. 29.77 + 19 =
  30. 30.67 + 29 =
  31. 31.12 + 29 =
  32. 32.22 − 19 =
  33. 33.20 − 9 =
  34. 34.24 − 19 =
  35. 35.23 + 9 =
  36. 36.740 − 99 =
  37. 37.99 − 29 =
  38. 38.70 + 19 =
  39. 39.61 + 9 =
  40. 40.389 − 99 =

Answer key

  1. 73
  2. 715
  3. 692
  4. 230
  5. 35
  6. 92
  7. 391
  8. 44
  9. 546
  10. 69
  11. 671
  12. 223
  13. 477
  14. 64
  15. 708
  16. 88
  17. 76
  18. 82
  19. 509
  20. 50
  21. 512
  22. 42
  23. 200
  24. 89
  25. 36
  26. 39
  27. 253
  28. 693
  29. 96
  30. 96
  31. 41
  32. 3
  33. 11
  34. 5
  35. 32
  36. 641
  37. 70
  38. 89
  39. 70
  40. 290

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