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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 31 · 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.√72 to 1 decimal place? (a) 8.6 (b) 8.7 (c) 8.8 (d) 8.5
  2. 2.√51 to 1 decimal place? (a) 7.2 (b) 6.9 (c) 7.1 (d) 7.0
  3. 3.√29 to 1 decimal place? (a) 5.5 (b) 5.3 (c) 5.4 (d) 5.2
  4. 4.Best estimate of 4869 ÷ 78? (a) 61 (b) 6100 (c) 610
  5. 5.√48 to 1 decimal place? (a) 7.0 (b) 6.8 (c) 7.1 (d) 6.9
  6. 6.Best estimate of 1301 ÷ 21? (a) 65 (b) 6500 (c) 650
  7. 7.√59 to 1 decimal place? (a) 7.5 (b) 7.7 (c) 7.6 (d) 7.8
  8. 8.√70 to 1 decimal place? (a) 8.4 (b) 8.1 (c) 8.2 (d) 8.3
  9. 9.Best estimate of 2009 ÷ 42? (a) 50 (b) 5000 (c) 500
  10. 10.Best estimate of 1731 ÷ 73? (a) 250 (b) 25 (c) 2500
  11. 11.Best estimate of 1015 ÷ 36? (a) 2500 (b) 250 (c) 25
  12. 12.Best estimate of 1908 ÷ 61? (a) 32 (b) 320 (c) 3200
  13. 13.Best estimate of 2576 ÷ 76? (a) 3200 (b) 320 (c) 32
  14. 14.Best estimate of 3469 ÷ 72? (a) 50 (b) 500 (c) 5000
  15. 15.Best estimate of 6353 ÷ 83? (a) 7900 (b) 790 (c) 79
  16. 16.Best estimate of 4246 ÷ 62? (a) 7100 (b) 710 (c) 71
  17. 17.Best estimate of 736 ÷ 28? (a) 2500 (b) 25 (c) 250
  18. 18.Best estimate of 1106 ÷ 32? (a) 370 (b) 3700 (c) 37
  19. 19.√31 to 1 decimal place? (a) 5.7 (b) 5.8 (c) 5.6 (d) 5.5
  20. 20.Best estimate of 1602 ÷ 41? (a) 4000 (b) 40 (c) 400
  21. 21.Best estimate of 1210 ÷ 82? (a) 1500 (b) 150 (c) 15
  22. 22.Best estimate of 758 ÷ 46? (a) 15 (b) 1500 (c) 150
  23. 23.√28 to 1 decimal place? (a) 5.6 (b) 5.3 (c) 5.5 (d) 5.4
  24. 24.√63 to 1 decimal place? (a) 8.0 (b) 8.1 (c) 7.8 (d) 7.9
  25. 25.Best estimate of 1695 ÷ 21? (a) 850 (b) 8500 (c) 85
  26. 26.√96 to 1 decimal place? (a) 10.1 (b) 10.0 (c) 9.8 (d) 9.9
  27. 27.Best estimate of 7446 ÷ 86? (a) 83 (b) 8300 (c) 830
  28. 28.Best estimate of 4094 ÷ 46? (a) 82 (b) 820 (c) 8200
  29. 29.Best estimate of 7332 ÷ 89? (a) 8100 (b) 81 (c) 810
  30. 30.Best estimate of 966 ÷ 52? (a) 190 (b) 19 (c) 1900
  31. 31.Best estimate of 569 ÷ 34? (a) 1900 (b) 19 (c) 190
  32. 32.√94 to 1 decimal place? (a) 9.5 (b) 9.7 (c) 9.4 (d) 9.6
  33. 33.√30 to 1 decimal place? (a) 5.6 (b) 5.8 (c) 5.7 (d) 5.5
  34. 34.Best estimate of 2930 ÷ 36? (a) 7300 (b) 73 (c) 730
  35. 35.√98 to 1 decimal place? (a) 10.1 (b) 10.0 (c) 10.2 (d) 9.9
  36. 36.Best estimate of 2167 ÷ 44? (a) 5400 (b) 54 (c) 540
  37. 37.√71 to 1 decimal place? (a) 8.4 (b) 8.3 (c) 8.2 (d) 8.1
  38. 38.√26 to 1 decimal place? (a) 5.1 (b) 5.0 (c) 5.2 (d) 5.3
  39. 39.Best estimate of 5119 ÷ 56? (a) 850 (b) 85 (c) 8500
  40. 40.Best estimate of 4145 ÷ 68? (a) 5900 (b) 59 (c) 590

Answer key

  1. 8.5
  2. 7.1
  3. 5.4
  4. 61
  5. 6.9
  6. 65
  7. 7.7
  8. 8.4
  9. 50
  10. 25
  11. 25
  12. 32
  13. 32
  14. 50
  15. 79
  16. 71
  17. 25
  18. 37
  19. 5.6
  20. 40
  21. 15
  22. 15
  23. 5.3
  24. 7.9
  25. 85
  26. 9.8
  27. 83
  28. 82
  29. 81
  30. 19
  31. 19
  32. 9.7
  33. 5.5
  34. 73
  35. 9.9
  36. 54
  37. 8.4
  38. 5.1
  39. 85
  40. 59

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