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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 357 · 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.√96 to 1 decimal place? (a) 10.1 (b) 9.9 (c) 10.0 (d) 9.8
  2. 2.√48 to 1 decimal place? (a) 7.0 (b) 6.8 (c) 7.1 (d) 6.9
  3. 3.Best estimate of 825 ÷ 26? (a) 28 (b) 280 (c) 2800
  4. 4.Best estimate of 1908 ÷ 68? (a) 27 (b) 270 (c) 2700
  5. 5.Best estimate of 4004 ÷ 72? (a) 5700 (b) 570 (c) 57
  6. 6.√70 to 1 decimal place? (a) 8.4 (b) 8.7 (c) 8.5 (d) 8.6
  7. 7.√84 to 1 decimal place? (a) 9.3 (b) 9.1 (c) 9.2 (d) 9.4
  8. 8.√20 to 1 decimal place? (a) 4.5 (b) 4.3 (c) 4.2 (d) 4.4
  9. 9.√58 to 1 decimal place? (a) 7.6 (b) 7.7 (c) 7.8 (d) 7.5
  10. 10.√71 to 1 decimal place? (a) 8.4 (b) 8.6 (c) 8.5 (d) 8.7
  11. 11.√22 to 1 decimal place? (a) 4.7 (b) 4.8 (c) 4.6 (d) 4.9
  12. 12.Best estimate of 5541 ÷ 62? (a) 920 (b) 92 (c) 9200
  13. 13.√80 to 1 decimal place? (a) 8.9 (b) 9.1 (c) 8.8 (d) 9.0
  14. 14.√26 to 1 decimal place? (a) 5.3 (b) 5.1 (c) 5.4 (d) 5.2
  15. 15.Best estimate of 2816 ÷ 79? (a) 35 (b) 3500 (c) 350
  16. 16.Best estimate of 1186 ÷ 36? (a) 300 (b) 3000 (c) 30
  17. 17.Best estimate of 5958 ÷ 67? (a) 8500 (b) 850 (c) 85
  18. 18.Best estimate of 5044 ÷ 87? (a) 56 (b) 5600 (c) 560
  19. 19.Best estimate of 3699 ÷ 42? (a) 9200 (b) 920 (c) 92
  20. 20.Best estimate of 4611 ÷ 54? (a) 92 (b) 920 (c) 9200
  21. 21.Best estimate of 859 ÷ 42? (a) 21 (b) 2100 (c) 210
  22. 22.Best estimate of 3875 ÷ 47? (a) 7800 (b) 780 (c) 78
  23. 23.√45 to 1 decimal place? (a) 6.7 (b) 6.8 (c) 6.9 (d) 6.6
  24. 24.Best estimate of 6334 ÷ 68? (a) 90 (b) 9000 (c) 900
  25. 25.Best estimate of 2377 ÷ 28? (a) 79 (b) 790 (c) 7900
  26. 26.√69 to 1 decimal place? (a) 8.1 (b) 8.2 (c) 8.4 (d) 8.3
  27. 27.Best estimate of 1465 ÷ 44? (a) 370 (b) 3700 (c) 37
  28. 28.√65 to 1 decimal place? (a) 8.1 (b) 8.0 (c) 7.9 (d) 8.2
  29. 29.Best estimate of 1862 ÷ 73? (a) 27 (b) 270 (c) 2700
  30. 30.√21 to 1 decimal place? (a) 4.7 (b) 4.8 (c) 4.9 (d) 4.6
  31. 31.Best estimate of 1905 ÷ 61? (a) 3200 (b) 320 (c) 32
  32. 32.√94 to 1 decimal place? (a) 10.0 (b) 9.8 (c) 9.9 (d) 9.7
  33. 33.Best estimate of 3413 ÷ 37? (a) 8500 (b) 85 (c) 850
  34. 34.√51 to 1 decimal place? (a) 7.2 (b) 7.3 (c) 7.1 (d) 7.0
  35. 35.Best estimate of 1685 ÷ 23? (a) 8400 (b) 84 (c) 840
  36. 36.√87 to 1 decimal place? (a) 9.0 (b) 9.3 (c) 9.1 (d) 9.2
  37. 37.√37 to 1 decimal place? (a) 5.8 (b) 6.0 (c) 5.9 (d) 6.1
  38. 38.Best estimate of 2135 ÷ 52? (a) 43 (b) 430 (c) 4300
  39. 39.Best estimate of 2902 ÷ 66? (a) 410 (b) 4100 (c) 41
  40. 40.Best estimate of 4205 ÷ 74? (a) 6000 (b) 60 (c) 600

Answer key

  1. 9.8
  2. 6.9
  3. 28
  4. 27
  5. 57
  6. 8.4
  7. 9.2
  8. 4.5
  9. 7.6
  10. 8.4
  11. 4.7
  12. 92
  13. 8.9
  14. 5.1
  15. 35
  16. 30
  17. 85
  18. 56
  19. 92
  20. 92
  21. 21
  22. 78
  23. 6.7
  24. 90
  25. 79
  26. 8.3
  27. 37
  28. 8.1
  29. 27
  30. 4.6
  31. 32
  32. 9.7
  33. 85
  34. 7.1
  35. 84
  36. 9.3
  37. 6.1
  38. 43
  39. 41
  40. 60

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