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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 411 · 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.√41 to 1 decimal place? (a) 6.5 (b) 6.4 (c) 6.2 (d) 6.3
  2. 2.√86 to 1 decimal place? (a) 9.5 (b) 9.6 (c) 9.4 (d) 9.3
  3. 3.Best estimate of 5596 ÷ 67? (a) 800 (b) 8000 (c) 80
  4. 4.Best estimate of 4768 ÷ 64? (a) 7900 (b) 79 (c) 790
  5. 5.Best estimate of 1120 ÷ 46? (a) 220 (b) 2200 (c) 22
  6. 6.√46 to 1 decimal place? (a) 6.7 (b) 6.8 (c) 6.9 (d) 7.0
  7. 7.√24 to 1 decimal place? (a) 4.8 (b) 5.0 (c) 4.9 (d) 4.7
  8. 8.Best estimate of 5846 ÷ 79? (a) 730 (b) 7300 (c) 73
  9. 9.Best estimate of 2330 ÷ 88? (a) 26 (b) 2600 (c) 260
  10. 10.√84 to 1 decimal place? (a) 9.2 (b) 9.0 (c) 8.9 (d) 9.1
  11. 11.Best estimate of 1271 ÷ 38? (a) 320 (b) 3200 (c) 32
  12. 12.Best estimate of 1869 ÷ 22? (a) 93 (b) 930 (c) 9300
  13. 13.√31 to 1 decimal place? (a) 5.7 (b) 5.5 (c) 5.4 (d) 5.6
  14. 14.Best estimate of 391 ÷ 32? (a) 13 (b) 1300 (c) 130
  15. 15.Best estimate of 6428 ÷ 81? (a) 800 (b) 8000 (c) 80
  16. 16.Best estimate of 2685 ÷ 32? (a) 900 (b) 9000 (c) 90
  17. 17.Best estimate of 836 ÷ 56? (a) 1400 (b) 140 (c) 14
  18. 18.√52 to 1 decimal place? (a) 7.3 (b) 7.5 (c) 7.2 (d) 7.4
  19. 19.√20 to 1 decimal place? (a) 4.3 (b) 4.5 (c) 4.6 (d) 4.4
  20. 20.√89 to 1 decimal place? (a) 9.5 (b) 9.3 (c) 9.4 (d) 9.6
  21. 21.Best estimate of 1229 ÷ 52? (a) 250 (b) 25 (c) 2500
  22. 22.Best estimate of 1631 ÷ 21? (a) 8200 (b) 820 (c) 82
  23. 23.√63 to 1 decimal place? (a) 8.0 (b) 7.7 (c) 7.9 (d) 7.8
  24. 24.√96 to 1 decimal place? (a) 9.9 (b) 9.8 (c) 10.1 (d) 10.0
  25. 25.Best estimate of 3091 ÷ 83? (a) 390 (b) 39 (c) 3900
  26. 26.Best estimate of 563 ÷ 33? (a) 1900 (b) 190 (c) 19
  27. 27.√87 to 1 decimal place? (a) 9.3 (b) 9.2 (c) 9.5 (d) 9.4
  28. 28.Best estimate of 2710 ÷ 43? (a) 6800 (b) 68 (c) 680
  29. 29.√59 to 1 decimal place? (a) 7.5 (b) 7.4 (c) 7.7 (d) 7.6
  30. 30.√82 to 1 decimal place? (a) 8.9 (b) 9.0 (c) 9.1 (d) 9.2
  31. 31.Best estimate of 1904 ÷ 82? (a) 2400 (b) 240 (c) 24
  32. 32.Best estimate of 6488 ÷ 83? (a) 81 (b) 8100 (c) 810
  33. 33.√71 to 1 decimal place? (a) 8.1 (b) 8.2 (c) 8.3 (d) 8.4
  34. 34.Best estimate of 6242 ÷ 69? (a) 8900 (b) 89 (c) 890
  35. 35.Best estimate of 1969 ÷ 29? (a) 66 (b) 6600 (c) 660
  36. 36.Best estimate of 1879 ÷ 21? (a) 9400 (b) 94 (c) 940
  37. 37.√26 to 1 decimal place? (a) 5.0 (b) 4.9 (c) 5.1 (d) 5.2
  38. 38.Best estimate of 5585 ÷ 76? (a) 7000 (b) 700 (c) 70
  39. 39.√74 to 1 decimal place? (a) 8.6 (b) 8.7 (c) 8.8 (d) 8.9
  40. 40.Best estimate of 4411 ÷ 72? (a) 6300 (b) 630 (c) 63

Answer key

  1. 6.4
  2. 9.3
  3. 80
  4. 79
  5. 22
  6. 6.8
  7. 4.9
  8. 73
  9. 26
  10. 9.2
  11. 32
  12. 93
  13. 5.6
  14. 13
  15. 80
  16. 90
  17. 14
  18. 7.2
  19. 4.5
  20. 9.4
  21. 25
  22. 82
  23. 7.9
  24. 9.8
  25. 39
  26. 19
  27. 9.3
  28. 68
  29. 7.7
  30. 9.1
  31. 24
  32. 81
  33. 8.4
  34. 89
  35. 66
  36. 94
  37. 5.1
  38. 70
  39. 8.6
  40. 63

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