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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 447 · 40 questions
TalentJR

How to do it in your head (Guess, divide, average): Division: round the divisor to the nearest ten and find the closest multiple of it. Square root: guess the nearest whole root, then divide the number by your guess. Average the guess and the answer of the division, and round to 1 decimal place.

NameDateTime takenScore ___ / 40
  1. 1.√28 to 1 decimal place? (a) 5.2 (b) 5.0 (c) 5.1 (d) 5.3
  2. 2.Best estimate of 3195 ÷ 46? (a) 64 (b) 640 (c) 6400
  3. 3.√61 to 1 decimal place? (a) 7.7 (b) 7.9 (c) 8.0 (d) 7.8
  4. 4.√50 to 1 decimal place? (a) 7.2 (b) 7.1 (c) 7.0 (d) 7.3
  5. 5.√47 to 1 decimal place? (a) 6.9 (b) 7.2 (c) 7.1 (d) 7.0
  6. 6.√58 to 1 decimal place? (a) 7.7 (b) 7.8 (c) 7.6 (d) 7.5
  7. 7.√65 to 1 decimal place? (a) 8.1 (b) 8.4 (c) 8.3 (d) 8.2
  8. 8.√78 to 1 decimal place? (a) 8.7 (b) 8.8 (c) 8.9 (d) 9.0
  9. 9.√55 to 1 decimal place? (a) 7.6 (b) 7.5 (c) 7.4 (d) 7.3
  10. 10.Best estimate of 3970 ÷ 82? (a) 50 (b) 500 (c) 5000
  11. 11.√96 to 1 decimal place? (a) 9.9 (b) 9.8 (c) 10.0 (d) 9.7
  12. 12.√71 to 1 decimal place? (a) 8.4 (b) 8.5 (c) 8.7 (d) 8.6
  13. 13.√38 to 1 decimal place? (a) 6.2 (b) 6.0 (c) 5.9 (d) 6.1
  14. 14.√42 to 1 decimal place? (a) 6.6 (b) 6.4 (c) 6.5 (d) 6.7
  15. 15.√59 to 1 decimal place? (a) 7.6 (b) 7.5 (c) 7.7 (d) 7.4
  16. 16.√37 to 1 decimal place? (a) 6.2 (b) 6.3 (c) 6.1 (d) 6.4
  17. 17.Best estimate of 1961 ÷ 77? (a) 250 (b) 25 (c) 2500
  18. 18.Best estimate of 1022 ÷ 38? (a) 260 (b) 2600 (c) 26
  19. 19.Best estimate of 931 ÷ 32? (a) 31 (b) 310 (c) 3100
  20. 20.Best estimate of 7353 ÷ 84? (a) 9200 (b) 920 (c) 92
  21. 21.Best estimate of 2902 ÷ 73? (a) 4100 (b) 410 (c) 41
  22. 22.Best estimate of 6138 ÷ 76? (a) 770 (b) 77 (c) 7700
  23. 23.√41 to 1 decimal place? (a) 6.3 (b) 6.4 (c) 6.1 (d) 6.2
  24. 24.Best estimate of 1136 ÷ 66? (a) 160 (b) 1600 (c) 16
  25. 25.√26 to 1 decimal place? (a) 5.3 (b) 5.4 (c) 5.1 (d) 5.2
  26. 26.Best estimate of 2501 ÷ 53? (a) 5000 (b) 50 (c) 500
  27. 27.Best estimate of 1587 ÷ 77? (a) 2000 (b) 20 (c) 200
  28. 28.√98 to 1 decimal place? (a) 9.9 (b) 10.2 (c) 10.0 (d) 10.1
  29. 29.Best estimate of 3220 ÷ 47? (a) 640 (b) 6400 (c) 64
  30. 30.Best estimate of 2794 ÷ 62? (a) 4700 (b) 470 (c) 47
  31. 31.Best estimate of 1600 ÷ 21? (a) 8000 (b) 800 (c) 80
  32. 32.Best estimate of 1595 ÷ 73? (a) 2300 (b) 23 (c) 230
  33. 33.Best estimate of 3060 ÷ 59? (a) 51 (b) 510 (c) 5100
  34. 34.Best estimate of 873 ÷ 57? (a) 15 (b) 150 (c) 1500
  35. 35.Best estimate of 5665 ÷ 82? (a) 710 (b) 7100 (c) 71
  36. 36.√92 to 1 decimal place? (a) 9.4 (b) 9.3 (c) 9.6 (d) 9.5
  37. 37.Best estimate of 6142 ÷ 66? (a) 88 (b) 8800 (c) 880
  38. 38.√69 to 1 decimal place? (a) 8.1 (b) 8.0 (c) 8.3 (d) 8.2
  39. 39.Best estimate of 1022 ÷ 21? (a) 510 (b) 51 (c) 5100
  40. 40.Best estimate of 3424 ÷ 36? (a) 860 (b) 86 (c) 8600

Answer key

  1. 5.3
  2. 64
  3. 7.8
  4. 7.1
  5. 6.9
  6. 7.6
  7. 8.1
  8. 8.8
  9. 7.4
  10. 50
  11. 9.8
  12. 8.4
  13. 6.2
  14. 6.5
  15. 7.7
  16. 6.1
  17. 25
  18. 26
  19. 31
  20. 92
  21. 41
  22. 77
  23. 6.4
  24. 16
  25. 5.1
  26. 50
  27. 20
  28. 9.9
  29. 64
  30. 47
  31. 80
  32. 23
  33. 51
  34. 15
  35. 71
  36. 9.6
  37. 88
  38. 8.3
  39. 51
  40. 86

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