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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 538 · 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. 1.45 + 29 =
  2. 2.899 − 99 =
  3. 3.25 − 9 =
  4. 4.32 − 29 =
  5. 5.26 − 9 =
  6. 6.241 + 99 =
  7. 7.74 − 9 =
  8. 8.63 − 9 =
  9. 9.749 + 99 =
  10. 10.36 + 29 =
  11. 11.84 − 29 =
  12. 12.73 − 9 =
  13. 13.93 − 29 =
  14. 14.25 + 29 =
  15. 15.86 − 19 =
  16. 16.35 + 9 =
  17. 17.700 + 99 =
  18. 18.67 − 19 =
  19. 19.107 − 29 =
  20. 20.472 − 99 =
  21. 21.624 − 99 =
  22. 22.61 + 9 =
  23. 23.23 + 9 =
  24. 24.29 + 19 =
  25. 25.48 + 9 =
  26. 26.40 + 9 =
  27. 27.43 + 19 =
  28. 28.138 + 99 =
  29. 29.247 − 99 =
  30. 30.55 + 9 =
  31. 31.68 + 29 =
  32. 32.17 − 9 =
  33. 33.54 − 9 =
  34. 34.44 − 19 =
  35. 35.33 − 29 =
  36. 36.315 + 99 =
  37. 37.40 + 19 =
  38. 38.62 + 9 =
  39. 39.591 − 99 =
  40. 40.63 + 19 =

Answer key

  1. 74
  2. 800
  3. 16
  4. 3
  5. 17
  6. 340
  7. 65
  8. 54
  9. 848
  10. 65
  11. 55
  12. 64
  13. 64
  14. 54
  15. 67
  16. 44
  17. 799
  18. 48
  19. 78
  20. 373
  21. 525
  22. 70
  23. 32
  24. 48
  25. 57
  26. 49
  27. 62
  28. 237
  29. 148
  30. 64
  31. 97
  32. 8
  33. 45
  34. 25
  35. 4
  36. 414
  37. 59
  38. 71
  39. 492
  40. 82

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