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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 67 · 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.√31 to 1 decimal place? (a) 5.6 (b) 5.7 (c) 5.5 (d) 5.8
  2. 2.√50 to 1 decimal place? (a) 7.1 (b) 7.3 (c) 7.0 (d) 7.2
  3. 3.Best estimate of 880 ÷ 43? (a) 2200 (b) 22 (c) 220
  4. 4.Best estimate of 3358 ÷ 82? (a) 42 (b) 420 (c) 4200
  5. 5.√62 to 1 decimal place? (a) 7.9 (b) 7.8 (c) 8.0 (d) 7.7
  6. 6.Best estimate of 1715 ÷ 26? (a) 57 (b) 5700 (c) 570
  7. 7.√61 to 1 decimal place? (a) 7.6 (b) 7.5 (c) 7.8 (d) 7.7
  8. 8.√58 to 1 decimal place? (a) 7.6 (b) 7.5 (c) 7.8 (d) 7.7
  9. 9.Best estimate of 1047 ÷ 87? (a) 120 (b) 12 (c) 1200
  10. 10.√89 to 1 decimal place? (a) 9.5 (b) 9.4 (c) 9.7 (d) 9.6
  11. 11.Best estimate of 5991 ÷ 71? (a) 8600 (b) 860 (c) 86
  12. 12.Best estimate of 2583 ÷ 66? (a) 37 (b) 370 (c) 3700
  13. 13.√34 to 1 decimal place? (a) 5.6 (b) 5.8 (c) 5.7 (d) 5.5
  14. 14.√21 to 1 decimal place? (a) 4.5 (b) 4.6 (c) 4.7 (d) 4.8
  15. 15.√30 to 1 decimal place? (a) 5.4 (b) 5.3 (c) 5.5 (d) 5.6
  16. 16.√74 to 1 decimal place? (a) 8.7 (b) 8.9 (c) 8.6 (d) 8.8
  17. 17.√69 to 1 decimal place? (a) 8.2 (b) 8.4 (c) 8.3 (d) 8.5
  18. 18.Best estimate of 2244 ÷ 56? (a) 37 (b) 3700 (c) 370
  19. 19.Best estimate of 529 ÷ 31? (a) 180 (b) 18 (c) 1800
  20. 20.Best estimate of 1668 ÷ 47? (a) 330 (b) 33 (c) 3300
  21. 21.Best estimate of 7371 ÷ 82? (a) 9200 (b) 920 (c) 92
  22. 22.√24 to 1 decimal place? (a) 4.9 (b) 5.0 (c) 5.1 (d) 4.8
  23. 23.Best estimate of 3583 ÷ 78? (a) 450 (b) 4500 (c) 45
  24. 24.Best estimate of 2526 ÷ 66? (a) 3600 (b) 360 (c) 36
  25. 25.Best estimate of 6559 ÷ 79? (a) 8200 (b) 82 (c) 820
  26. 26.Best estimate of 1325 ÷ 62? (a) 220 (b) 22 (c) 2200
  27. 27.Best estimate of 1936 ÷ 46? (a) 39 (b) 390 (c) 3900
  28. 28.√87 to 1 decimal place? (a) 9.1 (b) 9.0 (c) 9.3 (d) 9.2
  29. 29.Best estimate of 2935 ÷ 36? (a) 73 (b) 7300 (c) 730
  30. 30.Best estimate of 1884 ÷ 46? (a) 380 (b) 3800 (c) 38
  31. 31.√38 to 1 decimal place? (a) 6.0 (b) 5.9 (c) 6.2 (d) 6.1
  32. 32.Best estimate of 3683 ÷ 62? (a) 610 (b) 61 (c) 6100
  33. 33.√22 to 1 decimal place? (a) 4.6 (b) 4.7 (c) 4.8 (d) 4.9
  34. 34.√80 to 1 decimal place? (a) 8.9 (b) 8.8 (c) 8.6 (d) 8.7
  35. 35.√88 to 1 decimal place? (a) 9.2 (b) 9.3 (c) 9.5 (d) 9.4
  36. 36.Best estimate of 3095 ÷ 86? (a) 340 (b) 34 (c) 3400
  37. 37.Best estimate of 3337 ÷ 47? (a) 670 (b) 67 (c) 6700
  38. 38.Best estimate of 1178 ÷ 61? (a) 200 (b) 20 (c) 2000
  39. 39.Best estimate of 3160 ÷ 39? (a) 790 (b) 7900 (c) 79
  40. 40.Best estimate of 397 ÷ 29? (a) 1300 (b) 130 (c) 13

Answer key

  1. 5.6
  2. 7.1
  3. 22
  4. 42
  5. 7.9
  6. 57
  7. 7.8
  8. 7.6
  9. 12
  10. 9.4
  11. 86
  12. 37
  13. 5.8
  14. 4.6
  15. 5.5
  16. 8.6
  17. 8.3
  18. 37
  19. 18
  20. 33
  21. 92
  22. 4.9
  23. 45
  24. 36
  25. 82
  26. 22
  27. 39
  28. 9.3
  29. 73
  30. 38
  31. 6.2
  32. 61
  33. 4.7
  34. 8.9
  35. 9.4
  36. 34
  37. 67
  38. 20
  39. 79
  40. 13

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