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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 451 · 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.√27 to 1 decimal place? (a) 5.5 (b) 5.2 (c) 5.4 (d) 5.3
  2. 2.√80 to 1 decimal place? (a) 9.2 (b) 9.1 (c) 8.9 (d) 9.0
  3. 3.Best estimate of 2302 ÷ 32? (a) 7700 (b) 770 (c) 77
  4. 4.√98 to 1 decimal place? (a) 10.0 (b) 10.1 (c) 9.9 (d) 10.2
  5. 5.Best estimate of 2390 ÷ 79? (a) 300 (b) 3000 (c) 30
  6. 6.√42 to 1 decimal place? (a) 6.7 (b) 6.4 (c) 6.6 (d) 6.5
  7. 7.√20 to 1 decimal place? (a) 4.2 (b) 4.5 (c) 4.4 (d) 4.3
  8. 8.Best estimate of 4143 ÷ 84? (a) 520 (b) 52 (c) 5200
  9. 9.√92 to 1 decimal place? (a) 9.4 (b) 9.6 (c) 9.5 (d) 9.3
  10. 10.Best estimate of 3297 ÷ 89? (a) 370 (b) 3700 (c) 37
  11. 11.Best estimate of 3296 ÷ 41? (a) 8200 (b) 820 (c) 82
  12. 12.Best estimate of 788 ÷ 48? (a) 16 (b) 1600 (c) 160
  13. 13.Best estimate of 956 ÷ 54? (a) 190 (b) 19 (c) 1900
  14. 14.Best estimate of 517 ÷ 42? (a) 130 (b) 1300 (c) 13
  15. 15.Best estimate of 2280 ÷ 42? (a) 570 (b) 57 (c) 5700
  16. 16.Best estimate of 6053 ÷ 86? (a) 67 (b) 670 (c) 6700
  17. 17.Best estimate of 1682 ÷ 41? (a) 4200 (b) 42 (c) 420
  18. 18.Best estimate of 567 ÷ 47? (a) 110 (b) 1100 (c) 11
  19. 19.√30 to 1 decimal place? (a) 5.7 (b) 5.8 (c) 5.5 (d) 5.6
  20. 20.Best estimate of 709 ÷ 34? (a) 240 (b) 2400 (c) 24
  21. 21.Best estimate of 3799 ÷ 63? (a) 630 (b) 6300 (c) 63
  22. 22.Best estimate of 4236 ÷ 79? (a) 53 (b) 5300 (c) 530
  23. 23.Best estimate of 4819 ÷ 66? (a) 6900 (b) 69 (c) 690
  24. 24.Best estimate of 2338 ÷ 26? (a) 780 (b) 7800 (c) 78
  25. 25.√34 to 1 decimal place? (a) 5.5 (b) 5.6 (c) 5.7 (d) 5.8
  26. 26.√50 to 1 decimal place? (a) 6.9 (b) 7.0 (c) 7.1 (d) 7.2
  27. 27.√38 to 1 decimal place? (a) 6.0 (b) 6.1 (c) 6.2 (d) 5.9
  28. 28.Best estimate of 1053 ÷ 28? (a) 3500 (b) 35 (c) 350
  29. 29.Best estimate of 3489 ÷ 86? (a) 390 (b) 39 (c) 3900
  30. 30.√55 to 1 decimal place? (a) 7.2 (b) 7.3 (c) 7.1 (d) 7.4
  31. 31.Best estimate of 4934 ÷ 72? (a) 7000 (b) 70 (c) 700
  32. 32.√29 to 1 decimal place? (a) 5.5 (b) 5.4 (c) 5.6 (d) 5.7
  33. 33.Best estimate of 6329 ÷ 82? (a) 7900 (b) 790 (c) 79
  34. 34.Best estimate of 1097 ÷ 79? (a) 1400 (b) 14 (c) 140
  35. 35.√77 to 1 decimal place? (a) 8.8 (b) 8.7 (c) 8.5 (d) 8.6
  36. 36.Best estimate of 1445 ÷ 24? (a) 7200 (b) 72 (c) 720
  37. 37.Best estimate of 642 ÷ 36? (a) 1600 (b) 16 (c) 160
  38. 38.Best estimate of 1990 ÷ 27? (a) 66 (b) 660 (c) 6600
  39. 39.√66 to 1 decimal place? (a) 7.9 (b) 8.0 (c) 8.1 (d) 7.8
  40. 40.Best estimate of 3365 ÷ 39? (a) 8400 (b) 84 (c) 840

Answer key

  1. 5.2
  2. 8.9
  3. 77
  4. 9.9
  5. 30
  6. 6.5
  7. 4.5
  8. 52
  9. 9.6
  10. 37
  11. 82
  12. 16
  13. 19
  14. 13
  15. 57
  16. 67
  17. 42
  18. 11
  19. 5.5
  20. 24
  21. 63
  22. 53
  23. 69
  24. 78
  25. 5.8
  26. 7.1
  27. 6.2
  28. 35
  29. 39
  30. 7.4
  31. 70
  32. 5.4
  33. 79
  34. 14
  35. 8.8
  36. 72
  37. 16
  38. 66
  39. 8.1
  40. 84

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