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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 345 · 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.√61 to 1 decimal place? (a) 7.7 (b) 7.8 (c) 8.0 (d) 7.9
  2. 2.√86 to 1 decimal place? (a) 9.5 (b) 9.3 (c) 9.6 (d) 9.4
  3. 3.Best estimate of 3047 ÷ 62? (a) 510 (b) 51 (c) 5100
  4. 4.Best estimate of 3814 ÷ 83? (a) 4800 (b) 48 (c) 480
  5. 5.Best estimate of 1899 ÷ 82? (a) 240 (b) 2400 (c) 24
  6. 6.√40 to 1 decimal place? (a) 6.3 (b) 6.1 (c) 6.0 (d) 6.2
  7. 7.√76 to 1 decimal place? (a) 8.8 (b) 8.9 (c) 8.7 (d) 8.6
  8. 8.Best estimate of 640 ÷ 36? (a) 160 (b) 1600 (c) 16
  9. 9.√59 to 1 decimal place? (a) 7.6 (b) 7.8 (c) 7.9 (d) 7.7
  10. 10.Best estimate of 3606 ÷ 42? (a) 900 (b) 9000 (c) 90
  11. 11.Best estimate of 1383 ÷ 69? (a) 20 (b) 200 (c) 2000
  12. 12.√94 to 1 decimal place? (a) 9.7 (b) 9.8 (c) 9.9 (d) 9.6
  13. 13.Best estimate of 2719 ÷ 74? (a) 39 (b) 3900 (c) 390
  14. 14.Best estimate of 4493 ÷ 78? (a) 5600 (b) 56 (c) 560
  15. 15.Best estimate of 612 ÷ 36? (a) 150 (b) 1500 (c) 15
  16. 16.Best estimate of 2006 ÷ 27? (a) 6700 (b) 670 (c) 67
  17. 17.Best estimate of 3927 ÷ 61? (a) 6500 (b) 650 (c) 65
  18. 18.√83 to 1 decimal place? (a) 9.3 (b) 9.1 (c) 9.4 (d) 9.2
  19. 19.√29 to 1 decimal place? (a) 5.4 (b) 5.3 (c) 5.5 (d) 5.6
  20. 20.√21 to 1 decimal place? (a) 4.5 (b) 4.6 (c) 4.7 (d) 4.4
  21. 21.√28 to 1 decimal place? (a) 5.5 (b) 5.6 (c) 5.4 (d) 5.3
  22. 22.√45 to 1 decimal place? (a) 6.9 (b) 6.7 (c) 6.6 (d) 6.8
  23. 23.√77 to 1 decimal place? (a) 9.0 (b) 8.8 (c) 8.7 (d) 8.9
  24. 24.Best estimate of 2607 ÷ 28? (a) 8700 (b) 870 (c) 87
  25. 25.Best estimate of 2463 ÷ 48? (a) 4900 (b) 490 (c) 49
  26. 26.√31 to 1 decimal place? (a) 5.7 (b) 5.8 (c) 5.9 (d) 5.6
  27. 27.Best estimate of 1866 ÷ 38? (a) 4700 (b) 47 (c) 470
  28. 28.√41 to 1 decimal place? (a) 6.3 (b) 6.6 (c) 6.4 (d) 6.5
  29. 29.Best estimate of 875 ÷ 26? (a) 290 (b) 2900 (c) 29
  30. 30.√23 to 1 decimal place? (a) 5.1 (b) 5.0 (c) 4.9 (d) 4.8
  31. 31.Best estimate of 1381 ÷ 48? (a) 280 (b) 28 (c) 2800
  32. 32.√56 to 1 decimal place? (a) 7.4 (b) 7.2 (c) 7.5 (d) 7.3
  33. 33.√82 to 1 decimal place? (a) 9.2 (b) 9.3 (c) 9.1 (d) 9.0
  34. 34.Best estimate of 1300 ÷ 69? (a) 1900 (b) 190 (c) 19
  35. 35.Best estimate of 3224 ÷ 42? (a) 810 (b) 8100 (c) 81
  36. 36.√27 to 1 decimal place? (a) 5.2 (b) 5.1 (c) 5.3 (d) 5.0
  37. 37.Best estimate of 2390 ÷ 72? (a) 3400 (b) 34 (c) 340
  38. 38.√92 to 1 decimal place? (a) 9.9 (b) 9.7 (c) 9.8 (d) 9.6
  39. 39.Best estimate of 5101 ÷ 74? (a) 73 (b) 730 (c) 7300
  40. 40.Best estimate of 1052 ÷ 58? (a) 18 (b) 180 (c) 1800

Answer key

  1. 7.8
  2. 9.3
  3. 51
  4. 48
  5. 24
  6. 6.3
  7. 8.7
  8. 16
  9. 7.7
  10. 90
  11. 20
  12. 9.7
  13. 39
  14. 56
  15. 15
  16. 67
  17. 65
  18. 9.1
  19. 5.4
  20. 4.6
  21. 5.3
  22. 6.7
  23. 8.8
  24. 87
  25. 49
  26. 5.6
  27. 47
  28. 6.4
  29. 29
  30. 4.8
  31. 28
  32. 7.5
  33. 9.1
  34. 19
  35. 81
  36. 5.2
  37. 34
  38. 9.6
  39. 73
  40. 18

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