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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 684 · 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. 1.80 + 19 =
  2. 2.79 − 29 =
  3. 3.328 + 99 =
  4. 4.68 + 9 =
  5. 5.76 + 19 =
  6. 6.45 − 29 =
  7. 7.58 − 9 =
  8. 8.24 + 19 =
  9. 9.59 − 19 =
  10. 10.52 + 29 =
  11. 11.95 − 19 =
  12. 12.89 − 29 =
  13. 13.55 + 29 =
  14. 14.76 − 9 =
  15. 15.73 + 19 =
  16. 16.423 + 99 =
  17. 17.19 + 9 =
  18. 18.274 − 99 =
  19. 19.41 + 9 =
  20. 20.92 − 19 =
  21. 21.37 + 19 =
  22. 22.48 + 19 =
  23. 23.154 − 99 =
  24. 24.29 + 9 =
  25. 25.54 − 9 =
  26. 26.63 − 29 =
  27. 27.384 + 99 =
  28. 28.330 + 99 =
  29. 29.58 + 19 =
  30. 30.15 + 19 =
  31. 31.82 − 19 =
  32. 32.42 + 19 =
  33. 33.216 + 99 =
  34. 34.513 − 99 =
  35. 35.36 + 9 =
  36. 36.36 − 9 =
  37. 37.47 − 9 =
  38. 38.33 + 9 =
  39. 39.102 − 29 =
  40. 40.57 + 9 =

Answer key

  1. 99
  2. 50
  3. 427
  4. 77
  5. 95
  6. 16
  7. 49
  8. 43
  9. 40
  10. 81
  11. 76
  12. 60
  13. 84
  14. 67
  15. 92
  16. 522
  17. 28
  18. 175
  19. 50
  20. 73
  21. 56
  22. 67
  23. 55
  24. 38
  25. 45
  26. 34
  27. 483
  28. 429
  29. 77
  30. 34
  31. 63
  32. 61
  33. 315
  34. 414
  35. 45
  36. 27
  37. 38
  38. 42
  39. 73
  40. 66

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