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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 61 · 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.√92 to 1 decimal place? (a) 9.8 (b) 9.7 (c) 9.9 (d) 9.6
  2. 2.Best estimate of 5179 ÷ 83? (a) 6500 (b) 65 (c) 650
  3. 3.√20 to 1 decimal place? (a) 4.5 (b) 4.3 (c) 4.6 (d) 4.4
  4. 4.Best estimate of 3098 ÷ 43? (a) 77 (b) 770 (c) 7700
  5. 5.Best estimate of 521 ÷ 41? (a) 13 (b) 1300 (c) 130
  6. 6.√98 to 1 decimal place? (a) 9.7 (b) 9.9 (c) 9.6 (d) 9.8
  7. 7.Best estimate of 1984 ÷ 32? (a) 660 (b) 66 (c) 6600
  8. 8.√28 to 1 decimal place? (a) 5.3 (b) 5.0 (c) 5.2 (d) 5.1
  9. 9.Best estimate of 3192 ÷ 42? (a) 8000 (b) 800 (c) 80
  10. 10.Best estimate of 3470 ÷ 43? (a) 870 (b) 87 (c) 8700
  11. 11.Best estimate of 6403 ÷ 89? (a) 71 (b) 710 (c) 7100
  12. 12.√35 to 1 decimal place? (a) 6.0 (b) 5.9 (c) 6.1 (d) 5.8
  13. 13.√21 to 1 decimal place? (a) 4.9 (b) 4.8 (c) 4.7 (d) 4.6
  14. 14.√50 to 1 decimal place? (a) 7.2 (b) 7.4 (c) 7.1 (d) 7.3
  15. 15.Best estimate of 2632 ÷ 89? (a) 290 (b) 2900 (c) 29
  16. 16.Best estimate of 1026 ÷ 62? (a) 17 (b) 1700 (c) 170
  17. 17.Best estimate of 2251 ÷ 56? (a) 3800 (b) 38 (c) 380
  18. 18.Best estimate of 892 ÷ 24? (a) 4500 (b) 450 (c) 45
  19. 19.√61 to 1 decimal place? (a) 7.7 (b) 7.8 (c) 7.6 (d) 7.5
  20. 20.√48 to 1 decimal place? (a) 7.0 (b) 6.9 (c) 7.2 (d) 7.1
  21. 21.√52 to 1 decimal place? (a) 7.0 (b) 7.2 (c) 7.1 (d) 7.3
  22. 22.Best estimate of 1415 ÷ 22? (a) 71 (b) 7100 (c) 710
  23. 23.√84 to 1 decimal place? (a) 9.2 (b) 9.1 (c) 9.0 (d) 9.3
  24. 24.√88 to 1 decimal place? (a) 9.2 (b) 9.1 (c) 9.4 (d) 9.3
  25. 25.Best estimate of 1480 ÷ 73? (a) 210 (b) 21 (c) 2100
  26. 26.Best estimate of 1454 ÷ 36? (a) 360 (b) 36 (c) 3600
  27. 27.Best estimate of 1483 ÷ 73? (a) 21 (b) 2100 (c) 210
  28. 28.Best estimate of 2324 ÷ 71? (a) 3300 (b) 33 (c) 330
  29. 29.Best estimate of 1222 ÷ 24? (a) 610 (b) 6100 (c) 61
  30. 30.√29 to 1 decimal place? (a) 5.5 (b) 5.4 (c) 5.2 (d) 5.3
  31. 31.Best estimate of 2072 ÷ 52? (a) 4100 (b) 410 (c) 41
  32. 32.√65 to 1 decimal place? (a) 8.3 (b) 8.4 (c) 8.2 (d) 8.1
  33. 33.Best estimate of 1759 ÷ 22? (a) 88 (b) 8800 (c) 880
  34. 34.Best estimate of 2577 ÷ 32? (a) 860 (b) 8600 (c) 86
  35. 35.√23 to 1 decimal place? (a) 4.8 (b) 5.0 (c) 4.7 (d) 4.9
  36. 36.√34 to 1 decimal place? (a) 5.9 (b) 5.7 (c) 6.0 (d) 5.8
  37. 37.Best estimate of 1380 ÷ 27? (a) 460 (b) 46 (c) 4600
  38. 38.Best estimate of 1668 ÷ 57? (a) 2800 (b) 280 (c) 28
  39. 39.Best estimate of 2658 ÷ 29? (a) 8900 (b) 89 (c) 890
  40. 40.Best estimate of 909 ÷ 58? (a) 1500 (b) 15 (c) 150

Answer key

  1. 9.6
  2. 65
  3. 4.5
  4. 77
  5. 13
  6. 9.9
  7. 66
  8. 5.3
  9. 80
  10. 87
  11. 71
  12. 5.9
  13. 4.6
  14. 7.1
  15. 29
  16. 17
  17. 38
  18. 45
  19. 7.8
  20. 6.9
  21. 7.2
  22. 71
  23. 9.2
  24. 9.4
  25. 21
  26. 36
  27. 21
  28. 33
  29. 61
  30. 5.4
  31. 41
  32. 8.1
  33. 88
  34. 86
  35. 4.8
  36. 5.8
  37. 46
  38. 28
  39. 89
  40. 15

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