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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 786 · 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.√26 to 1 decimal place? (a) 5.4 (b) 5.1 (c) 5.3 (d) 5.2
  2. 2.Best estimate of 1721 ÷ 23? (a) 8600 (b) 860 (c) 86
  3. 3.Best estimate of 3426 ÷ 49? (a) 690 (b) 69 (c) 6900
  4. 4.Best estimate of 1425 ÷ 76? (a) 180 (b) 1800 (c) 18
  5. 5.√84 to 1 decimal place? (a) 9.4 (b) 9.3 (c) 9.2 (d) 9.5
  6. 6.Best estimate of 631 ÷ 44? (a) 1600 (b) 160 (c) 16
  7. 7.√92 to 1 decimal place? (a) 9.5 (b) 9.8 (c) 9.6 (d) 9.7
  8. 8.Best estimate of 3053 ÷ 47? (a) 610 (b) 6100 (c) 61
  9. 9.Best estimate of 3679 ÷ 42? (a) 9200 (b) 92 (c) 920
  10. 10.√31 to 1 decimal place? (a) 5.5 (b) 5.8 (c) 5.6 (d) 5.7
  11. 11.√94 to 1 decimal place? (a) 9.6 (b) 9.4 (c) 9.7 (d) 9.5
  12. 12.√65 to 1 decimal place? (a) 8.1 (b) 8.2 (c) 8.3 (d) 8.4
  13. 13.√79 to 1 decimal place? (a) 9.0 (b) 8.8 (c) 9.1 (d) 8.9
  14. 14.Best estimate of 2671 ÷ 42? (a) 670 (b) 67 (c) 6700
  15. 15.√58 to 1 decimal place? (a) 7.9 (b) 7.7 (c) 7.6 (d) 7.8
  16. 16.Best estimate of 5272 ÷ 56? (a) 88 (b) 8800 (c) 880
  17. 17.√37 to 1 decimal place? (a) 6.0 (b) 6.1 (c) 6.3 (d) 6.2
  18. 18.Best estimate of 1083 ÷ 59? (a) 180 (b) 1800 (c) 18
  19. 19.Best estimate of 1247 ÷ 51? (a) 2500 (b) 25 (c) 250
  20. 20.√22 to 1 decimal place? (a) 4.9 (b) 4.7 (c) 4.6 (d) 4.8
  21. 21.Best estimate of 2840 ÷ 81? (a) 3600 (b) 36 (c) 360
  22. 22.√69 to 1 decimal place? (a) 8.4 (b) 8.3 (c) 8.6 (d) 8.5
  23. 23.√70 to 1 decimal place? (a) 8.5 (b) 8.4 (c) 8.6 (d) 8.7
  24. 24.Best estimate of 2348 ÷ 61? (a) 3900 (b) 390 (c) 39
  25. 25.√74 to 1 decimal place? (a) 8.4 (b) 8.6 (c) 8.7 (d) 8.5
  26. 26.√72 to 1 decimal place? (a) 8.7 (b) 8.5 (c) 8.4 (d) 8.6
  27. 27.Best estimate of 4861 ÷ 79? (a) 6100 (b) 610 (c) 61
  28. 28.√52 to 1 decimal place? (a) 7.0 (b) 7.1 (c) 7.2 (d) 7.3
  29. 29.√44 to 1 decimal place? (a) 6.7 (b) 6.8 (c) 6.6 (d) 6.9
  30. 30.Best estimate of 2785 ÷ 51? (a) 56 (b) 5600 (c) 560
  31. 31.Best estimate of 1943 ÷ 33? (a) 650 (b) 6500 (c) 65
  32. 32.Best estimate of 4449 ÷ 54? (a) 89 (b) 890 (c) 8900
  33. 33.Best estimate of 4099 ÷ 62? (a) 680 (b) 68 (c) 6800
  34. 34.Best estimate of 1019 ÷ 43? (a) 25 (b) 2500 (c) 250
  35. 35.Best estimate of 1394 ÷ 81? (a) 170 (b) 17 (c) 1700
  36. 36.Best estimate of 4259 ÷ 69? (a) 61 (b) 6100 (c) 610
  37. 37.√28 to 1 decimal place? (a) 5.0 (b) 5.1 (c) 5.2 (d) 5.3
  38. 38.√23 to 1 decimal place? (a) 4.6 (b) 4.9 (c) 4.7 (d) 4.8
  39. 39.√66 to 1 decimal place? (a) 8.0 (b) 8.2 (c) 7.9 (d) 8.1
  40. 40.Best estimate of 6453 ÷ 72? (a) 92 (b) 920 (c) 9200

Answer key

  1. 5.1
  2. 86
  3. 69
  4. 18
  5. 9.2
  6. 16
  7. 9.6
  8. 61
  9. 92
  10. 5.6
  11. 9.7
  12. 8.1
  13. 8.9
  14. 67
  15. 7.6
  16. 88
  17. 6.1
  18. 18
  19. 25
  20. 4.7
  21. 36
  22. 8.3
  23. 8.4
  24. 39
  25. 8.6
  26. 8.5
  27. 61
  28. 7.2
  29. 6.6
  30. 56
  31. 65
  32. 89
  33. 68
  34. 25
  35. 17
  36. 61
  37. 5.3
  38. 4.8
  39. 8.1
  40. 92

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