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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 678 · 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.√21 to 1 decimal place? (a) 4.6 (b) 4.4 (c) 4.5 (d) 4.7
  2. 2.√28 to 1 decimal place? (a) 5.0 (b) 5.2 (c) 5.3 (d) 5.1
  3. 3.Best estimate of 3239 ÷ 36? (a) 810 (b) 81 (c) 8100
  4. 4.√38 to 1 decimal place? (a) 6.0 (b) 6.3 (c) 6.1 (d) 6.2
  5. 5.√34 to 1 decimal place? (a) 5.8 (b) 6.1 (c) 5.9 (d) 6.0
  6. 6.Best estimate of 1734 ÷ 36? (a) 43 (b) 4300 (c) 430
  7. 7.Best estimate of 4757 ÷ 52? (a) 950 (b) 9500 (c) 95
  8. 8.Best estimate of 4479 ÷ 66? (a) 64 (b) 6400 (c) 640
  9. 9.Best estimate of 1169 ÷ 22? (a) 5800 (b) 58 (c) 580
  10. 10.Best estimate of 1199 ÷ 31? (a) 400 (b) 40 (c) 4000
  11. 11.Best estimate of 1968 ÷ 43? (a) 49 (b) 490 (c) 4900
  12. 12.√50 to 1 decimal place? (a) 7.2 (b) 7.0 (c) 7.1 (d) 6.9
  13. 13.Best estimate of 788 ÷ 42? (a) 20 (b) 2000 (c) 200
  14. 14.Best estimate of 2011 ÷ 33? (a) 67 (b) 670 (c) 6700
  15. 15.Best estimate of 1756 ÷ 26? (a) 59 (b) 5900 (c) 590
  16. 16.√37 to 1 decimal place? (a) 6.4 (b) 6.3 (c) 6.2 (d) 6.1
  17. 17.√96 to 1 decimal place? (a) 9.8 (b) 9.7 (c) 9.9 (d) 10.0
  18. 18.√55 to 1 decimal place? (a) 7.4 (b) 7.5 (c) 7.3 (d) 7.2
  19. 19.√85 to 1 decimal place? (a) 9.0 (b) 9.2 (c) 8.9 (d) 9.1
  20. 20.Best estimate of 3275 ÷ 66? (a) 4700 (b) 47 (c) 470
  21. 21.√61 to 1 decimal place? (a) 7.5 (b) 7.6 (c) 7.7 (d) 7.8
  22. 22.Best estimate of 4213 ÷ 73? (a) 600 (b) 6000 (c) 60
  23. 23.Best estimate of 935 ÷ 22? (a) 470 (b) 4700 (c) 47
  24. 24.Best estimate of 5597 ÷ 72? (a) 80 (b) 8000 (c) 800
  25. 25.Best estimate of 3362 ÷ 49? (a) 67 (b) 670 (c) 6700
  26. 26.√92 to 1 decimal place? (a) 9.5 (b) 9.6 (c) 9.7 (d) 9.8
  27. 27.√90 to 1 decimal place? (a) 9.5 (b) 9.8 (c) 9.6 (d) 9.7
  28. 28.Best estimate of 1537 ÷ 86? (a) 170 (b) 17 (c) 1700
  29. 29.√94 to 1 decimal place? (a) 9.9 (b) 9.7 (c) 9.6 (d) 9.8
  30. 30.√71 to 1 decimal place? (a) 8.3 (b) 8.5 (c) 8.2 (d) 8.4
  31. 31.Best estimate of 5909 ÷ 82? (a) 740 (b) 74 (c) 7400
  32. 32.√20 to 1 decimal place? (a) 4.8 (b) 4.6 (c) 4.5 (d) 4.7
  33. 33.√51 to 1 decimal place? (a) 7.2 (b) 7.1 (c) 7.3 (d) 7.4
  34. 34.Best estimate of 3880 ÷ 52? (a) 7800 (b) 78 (c) 780
  35. 35.Best estimate of 3150 ÷ 87? (a) 350 (b) 3500 (c) 35
  36. 36.Best estimate of 894 ÷ 29? (a) 30 (b) 300 (c) 3000
  37. 37.Best estimate of 5201 ÷ 66? (a) 7400 (b) 74 (c) 740
  38. 38.Best estimate of 3501 ÷ 89? (a) 39 (b) 3900 (c) 390
  39. 39.Best estimate of 1488 ÷ 33? (a) 500 (b) 50 (c) 5000
  40. 40.√78 to 1 decimal place? (a) 9.1 (b) 8.9 (c) 9.0 (d) 8.8

Answer key

  1. 4.6
  2. 5.3
  3. 81
  4. 6.2
  5. 5.8
  6. 43
  7. 95
  8. 64
  9. 58
  10. 40
  11. 49
  12. 7.1
  13. 20
  14. 67
  15. 59
  16. 6.1
  17. 9.8
  18. 7.4
  19. 9.2
  20. 47
  21. 7.8
  22. 60
  23. 47
  24. 80
  25. 67
  26. 9.6
  27. 9.5
  28. 17
  29. 9.7
  30. 8.4
  31. 74
  32. 4.5
  33. 7.1
  34. 78
  35. 35
  36. 30
  37. 74
  38. 39
  39. 50
  40. 8.8

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