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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 121 · 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.Best estimate of 1344 ÷ 72? (a) 190 (b) 1900 (c) 19
  2. 2.Best estimate of 5087 ÷ 74? (a) 730 (b) 7300 (c) 73
  3. 3.√47 to 1 decimal place? (a) 7.0 (b) 6.9 (c) 6.8 (d) 6.7
  4. 4.Best estimate of 2118 ÷ 42? (a) 5300 (b) 530 (c) 53
  5. 5.√50 to 1 decimal place? (a) 7.1 (b) 7.0 (c) 6.9 (d) 7.2
  6. 6.Best estimate of 2338 ÷ 32? (a) 7800 (b) 780 (c) 78
  7. 7.Best estimate of 345 ÷ 26? (a) 120 (b) 1200 (c) 12
  8. 8.√98 to 1 decimal place? (a) 9.9 (b) 10.0 (c) 9.7 (d) 9.8
  9. 9.Best estimate of 3224 ÷ 38? (a) 8100 (b) 81 (c) 810
  10. 10.√90 to 1 decimal place? (a) 9.6 (b) 9.7 (c) 9.4 (d) 9.5
  11. 11.Best estimate of 715 ÷ 32? (a) 2400 (b) 24 (c) 240
  12. 12.Best estimate of 3903 ÷ 58? (a) 650 (b) 65 (c) 6500
  13. 13.√58 to 1 decimal place? (a) 7.4 (b) 7.6 (c) 7.7 (d) 7.5
  14. 14.Best estimate of 2188 ÷ 23? (a) 10900 (b) 109 (c) 1090
  15. 15.Best estimate of 1782 ÷ 38? (a) 450 (b) 4500 (c) 45
  16. 16.Best estimate of 3894 ÷ 47? (a) 7800 (b) 780 (c) 78
  17. 17.Best estimate of 1513 ÷ 88? (a) 170 (b) 17 (c) 1700
  18. 18.√40 to 1 decimal place? (a) 6.5 (b) 6.3 (c) 6.4 (d) 6.2
  19. 19.Best estimate of 1670 ÷ 47? (a) 3300 (b) 330 (c) 33
  20. 20.√26 to 1 decimal place? (a) 4.8 (b) 5.1 (c) 4.9 (d) 5.0
  21. 21.√41 to 1 decimal place? (a) 6.4 (b) 6.6 (c) 6.3 (d) 6.5
  22. 22.Best estimate of 2042 ÷ 54? (a) 410 (b) 41 (c) 4100
  23. 23.Best estimate of 4394 ÷ 73? (a) 63 (b) 630 (c) 6300
  24. 24.Best estimate of 3898 ÷ 86? (a) 43 (b) 4300 (c) 430
  25. 25.√66 to 1 decimal place? (a) 8.0 (b) 8.3 (c) 8.1 (d) 8.2
  26. 26.Best estimate of 1003 ÷ 79? (a) 130 (b) 13 (c) 1300
  27. 27.√96 to 1 decimal place? (a) 9.9 (b) 9.6 (c) 9.7 (d) 9.8
  28. 28.Best estimate of 4242 ÷ 82? (a) 53 (b) 530 (c) 5300
  29. 29.Best estimate of 2665 ÷ 38? (a) 670 (b) 6700 (c) 67
  30. 30.Best estimate of 4234 ÷ 86? (a) 47 (b) 470 (c) 4700
  31. 31.√38 to 1 decimal place? (a) 6.1 (b) 6.2 (c) 5.9 (d) 6.0
  32. 32.√69 to 1 decimal place? (a) 8.6 (b) 8.3 (c) 8.4 (d) 8.5
  33. 33.√65 to 1 decimal place? (a) 8.2 (b) 8.3 (c) 8.1 (d) 8.0
  34. 34.Best estimate of 1495 ÷ 23? (a) 7500 (b) 750 (c) 75
  35. 35.Best estimate of 5577 ÷ 72? (a) 800 (b) 8000 (c) 80
  36. 36.Best estimate of 4972 ÷ 62? (a) 830 (b) 8300 (c) 83
  37. 37.Best estimate of 1535 ÷ 46? (a) 31 (b) 310 (c) 3100
  38. 38.Best estimate of 7560 ÷ 84? (a) 950 (b) 95 (c) 9500
  39. 39.√45 to 1 decimal place? (a) 6.8 (b) 6.9 (c) 6.7 (d) 6.6
  40. 40.Best estimate of 736 ÷ 32? (a) 250 (b) 2500 (c) 25

Answer key

  1. 19
  2. 73
  3. 6.9
  4. 53
  5. 7.1
  6. 78
  7. 12
  8. 9.9
  9. 81
  10. 9.5
  11. 24
  12. 65
  13. 7.6
  14. 109
  15. 45
  16. 78
  17. 17
  18. 6.3
  19. 33
  20. 5.1
  21. 6.4
  22. 41
  23. 63
  24. 43
  25. 8.1
  26. 13
  27. 9.8
  28. 53
  29. 67
  30. 47
  31. 6.2
  32. 8.3
  33. 8.1
  34. 75
  35. 80
  36. 83
  37. 31
  38. 95
  39. 6.7
  40. 25

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