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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 797 · 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.√40 to 1 decimal place? (a) 6.3 (b) 6.2 (c) 6.4 (d) 6.5
  2. 2.√50 to 1 decimal place? (a) 7.4 (b) 7.1 (c) 7.3 (d) 7.2
  3. 3.Best estimate of 640 ÷ 27? (a) 210 (b) 2100 (c) 21
  4. 4.√94 to 1 decimal place? (a) 10.0 (b) 9.8 (c) 9.7 (d) 9.9
  5. 5.Best estimate of 929 ÷ 46? (a) 19 (b) 190 (c) 1900
  6. 6.Best estimate of 905 ÷ 69? (a) 13 (b) 1300 (c) 130
  7. 7.√23 to 1 decimal place? (a) 5.0 (b) 4.9 (c) 4.8 (d) 4.7
  8. 8.√20 to 1 decimal place? (a) 4.4 (b) 4.7 (c) 4.5 (d) 4.6
  9. 9.Best estimate of 2820 ÷ 52? (a) 56 (b) 560 (c) 5600
  10. 10.Best estimate of 640 ÷ 33? (a) 21 (b) 2100 (c) 210
  11. 11.√34 to 1 decimal place? (a) 5.5 (b) 5.7 (c) 5.6 (d) 5.8
  12. 12.√92 to 1 decimal place? (a) 9.7 (b) 9.6 (c) 9.4 (d) 9.5
  13. 13.Best estimate of 2260 ÷ 44? (a) 5700 (b) 57 (c) 570
  14. 14.Best estimate of 2456 ÷ 51? (a) 4900 (b) 490 (c) 49
  15. 15.Best estimate of 4427 ÷ 79? (a) 55 (b) 5500 (c) 550
  16. 16.√37 to 1 decimal place? (a) 6.2 (b) 6.0 (c) 5.9 (d) 6.1
  17. 17.√51 to 1 decimal place? (a) 7.2 (b) 7.3 (c) 7.4 (d) 7.1
  18. 18.Best estimate of 1585 ÷ 87? (a) 18 (b) 180 (c) 1800
  19. 19.Best estimate of 7446 ÷ 78? (a) 930 (b) 9300 (c) 93
  20. 20.Best estimate of 2435 ÷ 71? (a) 3500 (b) 350 (c) 35
  21. 21.Best estimate of 2632 ÷ 86? (a) 29 (b) 2900 (c) 290
  22. 22.√53 to 1 decimal place? (a) 7.3 (b) 7.5 (c) 7.2 (d) 7.4
  23. 23.Best estimate of 1549 ÷ 36? (a) 390 (b) 39 (c) 3900
  24. 24.Best estimate of 1366 ÷ 72? (a) 2000 (b) 200 (c) 20
  25. 25.Best estimate of 1646 ÷ 86? (a) 180 (b) 18 (c) 1800
  26. 26.Best estimate of 4955 ÷ 61? (a) 8300 (b) 830 (c) 83
  27. 27.Best estimate of 2934 ÷ 41? (a) 730 (b) 7300 (c) 73
  28. 28.√96 to 1 decimal place? (a) 10.1 (b) 9.8 (c) 10.0 (d) 9.9
  29. 29.Best estimate of 948 ÷ 52? (a) 190 (b) 19 (c) 1900
  30. 30.Best estimate of 1397 ÷ 21? (a) 70 (b) 700 (c) 7000
  31. 31.Best estimate of 1617 ÷ 21? (a) 810 (b) 8100 (c) 81
  32. 32.√31 to 1 decimal place? (a) 5.8 (b) 5.9 (c) 5.7 (d) 5.6
  33. 33.Best estimate of 1202 ÷ 52? (a) 24 (b) 240 (c) 2400
  34. 34.Best estimate of 4522 ÷ 88? (a) 500 (b) 50 (c) 5000
  35. 35.√61 to 1 decimal place? (a) 8.0 (b) 7.8 (c) 7.9 (d) 8.1
  36. 36.√76 to 1 decimal place? (a) 8.7 (b) 8.6 (c) 8.9 (d) 8.8
  37. 37.Best estimate of 3695 ÷ 54? (a) 7400 (b) 740 (c) 74
  38. 38.Best estimate of 3501 ÷ 73? (a) 5000 (b) 50 (c) 500
  39. 39.Best estimate of 764 ÷ 46? (a) 15 (b) 1500 (c) 150
  40. 40.√43 to 1 decimal place? (a) 6.5 (b) 6.3 (c) 6.6 (d) 6.4

Answer key

  1. 6.3
  2. 7.1
  3. 21
  4. 9.7
  5. 19
  6. 13
  7. 4.8
  8. 4.5
  9. 56
  10. 21
  11. 5.8
  12. 9.6
  13. 57
  14. 49
  15. 55
  16. 6.1
  17. 7.1
  18. 18
  19. 93
  20. 35
  21. 29
  22. 7.3
  23. 39
  24. 20
  25. 18
  26. 83
  27. 73
  28. 9.8
  29. 19
  30. 70
  31. 81
  32. 5.6
  33. 24
  34. 50
  35. 7.8
  36. 8.7
  37. 74
  38. 50
  39. 15
  40. 6.6

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