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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 889 · 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.√86 to 1 decimal place? (a) 9.3 (b) 9.0 (c) 9.2 (d) 9.1
  2. 2.Best estimate of 2428 ÷ 53? (a) 4900 (b) 490 (c) 49
  3. 3.Best estimate of 814 ÷ 21? (a) 41 (b) 4100 (c) 410
  4. 4.Best estimate of 1310 ÷ 42? (a) 3300 (b) 33 (c) 330
  5. 5.Best estimate of 2764 ÷ 61? (a) 4600 (b) 46 (c) 460
  6. 6.√85 to 1 decimal place? (a) 9.3 (b) 9.4 (c) 9.2 (d) 9.1
  7. 7.Best estimate of 4914 ÷ 61? (a) 82 (b) 8200 (c) 820
  8. 8.√61 to 1 decimal place? (a) 7.8 (b) 7.7 (c) 8.0 (d) 7.9
  9. 9.Best estimate of 5811 ÷ 76? (a) 7300 (b) 730 (c) 73
  10. 10.Best estimate of 7130 ÷ 87? (a) 7900 (b) 790 (c) 79
  11. 11.Best estimate of 1473 ÷ 73? (a) 2100 (b) 21 (c) 210
  12. 12.√92 to 1 decimal place? (a) 9.6 (b) 9.4 (c) 9.3 (d) 9.5
  13. 13.Best estimate of 5508 ÷ 73? (a) 7900 (b) 79 (c) 790
  14. 14.Best estimate of 1849 ÷ 82? (a) 2300 (b) 23 (c) 230
  15. 15.Best estimate of 1004 ÷ 26? (a) 330 (b) 33 (c) 3300
  16. 16.Best estimate of 5676 ÷ 81? (a) 71 (b) 710 (c) 7100
  17. 17.Best estimate of 4297 ÷ 53? (a) 8600 (b) 860 (c) 86
  18. 18.√88 to 1 decimal place? (a) 9.3 (b) 9.6 (c) 9.4 (d) 9.5
  19. 19.√55 to 1 decimal place? (a) 7.6 (b) 7.5 (c) 7.4 (d) 7.7
  20. 20.√70 to 1 decimal place? (a) 8.3 (b) 8.2 (c) 8.1 (d) 8.4
  21. 21.Best estimate of 4572 ÷ 76? (a) 570 (b) 57 (c) 5700
  22. 22.√24 to 1 decimal place? (a) 5.2 (b) 5.1 (c) 4.9 (d) 5.0
  23. 23.Best estimate of 1556 ÷ 72? (a) 22 (b) 220 (c) 2200
  24. 24.Best estimate of 3280 ÷ 76? (a) 410 (b) 41 (c) 4100
  25. 25.√69 to 1 decimal place? (a) 8.1 (b) 8.4 (c) 8.2 (d) 8.3
  26. 26.√63 to 1 decimal place? (a) 8.2 (b) 7.9 (c) 8.1 (d) 8.0
  27. 27.√38 to 1 decimal place? (a) 6.2 (b) 6.3 (c) 6.0 (d) 6.1
  28. 28.√67 to 1 decimal place? (a) 8.2 (b) 8.4 (c) 8.3 (d) 8.1
  29. 29.√79 to 1 decimal place? (a) 9.0 (b) 8.9 (c) 9.1 (d) 9.2
  30. 30.√26 to 1 decimal place? (a) 5.2 (b) 5.0 (c) 5.1 (d) 4.9
  31. 31.√80 to 1 decimal place? (a) 9.1 (b) 9.0 (c) 9.2 (d) 8.9
  32. 32.Best estimate of 1213 ÷ 46? (a) 2400 (b) 240 (c) 24
  33. 33.√34 to 1 decimal place? (a) 6.0 (b) 5.7 (c) 5.9 (d) 5.8
  34. 34.Best estimate of 929 ÷ 77? (a) 1200 (b) 12 (c) 120
  35. 35.√46 to 1 decimal place? (a) 6.7 (b) 6.9 (c) 6.8 (d) 7.0
  36. 36.√78 to 1 decimal place? (a) 8.6 (b) 8.8 (c) 8.5 (d) 8.7
  37. 37.Best estimate of 2743 ÷ 31? (a) 910 (b) 9100 (c) 91
  38. 38.√50 to 1 decimal place? (a) 7.2 (b) 7.4 (c) 7.1 (d) 7.3
  39. 39.Best estimate of 1590 ÷ 68? (a) 2300 (b) 230 (c) 23
  40. 40.Best estimate of 4423 ÷ 51? (a) 8800 (b) 88 (c) 880

Answer key

  1. 9.3
  2. 49
  3. 41
  4. 33
  5. 46
  6. 9.2
  7. 82
  8. 7.8
  9. 73
  10. 79
  11. 21
  12. 9.6
  13. 79
  14. 23
  15. 33
  16. 71
  17. 86
  18. 9.4
  19. 7.4
  20. 8.4
  21. 57
  22. 4.9
  23. 22
  24. 41
  25. 8.3
  26. 7.9
  27. 6.2
  28. 8.2
  29. 8.9
  30. 5.1
  31. 8.9
  32. 24
  33. 5.8
  34. 12
  35. 6.8
  36. 8.8
  37. 91
  38. 7.1
  39. 23
  40. 88

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