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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 553 · 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.√55 to 1 decimal place? (a) 7.7 (b) 7.6 (c) 7.4 (d) 7.5
  2. 2.√80 to 1 decimal place? (a) 9.1 (b) 8.9 (c) 8.8 (d) 9.0
  3. 3.Best estimate of 3643 ÷ 42? (a) 91 (b) 9100 (c) 910
  4. 4.√98 to 1 decimal place? (a) 9.8 (b) 9.7 (c) 9.9 (d) 9.6
  5. 5.Best estimate of 1879 ÷ 81? (a) 230 (b) 2300 (c) 23
  6. 6.Best estimate of 955 ÷ 31? (a) 32 (b) 320 (c) 3200
  7. 7.√90 to 1 decimal place? (a) 9.3 (b) 9.5 (c) 9.2 (d) 9.4
  8. 8.√45 to 1 decimal place? (a) 6.6 (b) 6.5 (c) 6.4 (d) 6.7
  9. 9.Best estimate of 1562 ÷ 41? (a) 3900 (b) 390 (c) 39
  10. 10.√40 to 1 decimal place? (a) 6.3 (b) 6.5 (c) 6.6 (d) 6.4
  11. 11.Best estimate of 1084 ÷ 73? (a) 150 (b) 15 (c) 1500
  12. 12.Best estimate of 5257 ÷ 76? (a) 6600 (b) 66 (c) 660
  13. 13.Best estimate of 2653 ÷ 31? (a) 8800 (b) 88 (c) 880
  14. 14.Best estimate of 2991 ÷ 47? (a) 600 (b) 6000 (c) 60
  15. 15.Best estimate of 2341 ÷ 32? (a) 780 (b) 78 (c) 7800
  16. 16.Best estimate of 7479 ÷ 86? (a) 8300 (b) 830 (c) 83
  17. 17.√70 to 1 decimal place? (a) 8.3 (b) 8.2 (c) 8.4 (d) 8.1
  18. 18.√85 to 1 decimal place? (a) 9.4 (b) 9.2 (c) 9.5 (d) 9.3
  19. 19.Best estimate of 2600 ÷ 36? (a) 650 (b) 6500 (c) 65
  20. 20.Best estimate of 7289 ÷ 76? (a) 9100 (b) 910 (c) 91
  21. 21.√62 to 1 decimal place? (a) 8.0 (b) 7.9 (c) 7.7 (d) 7.8
  22. 22.Best estimate of 1018 ÷ 66? (a) 15 (b) 1500 (c) 150
  23. 23.√94 to 1 decimal place? (a) 9.8 (b) 9.5 (c) 9.6 (d) 9.7
  24. 24.√32 to 1 decimal place? (a) 6.0 (b) 5.9 (c) 5.7 (d) 5.8
  25. 25.√38 to 1 decimal place? (a) 6.1 (b) 6.0 (c) 6.2 (d) 6.3
  26. 26.Best estimate of 2470 ÷ 26? (a) 8200 (b) 82 (c) 820
  27. 27.Best estimate of 1449 ÷ 66? (a) 210 (b) 21 (c) 2100
  28. 28.Best estimate of 2779 ÷ 64? (a) 460 (b) 4600 (c) 46
  29. 29.Best estimate of 3929 ÷ 67? (a) 560 (b) 56 (c) 5600
  30. 30.√35 to 1 decimal place? (a) 5.8 (b) 6.1 (c) 6.0 (d) 5.9
  31. 31.Best estimate of 2969 ÷ 47? (a) 5900 (b) 590 (c) 59
  32. 32.Best estimate of 1233 ÷ 33? (a) 41 (b) 410 (c) 4100
  33. 33.Best estimate of 5919 ÷ 64? (a) 9900 (b) 99 (c) 990
  34. 34.Best estimate of 2043 ÷ 32? (a) 680 (b) 68 (c) 6800
  35. 35.Best estimate of 1188 ÷ 81? (a) 150 (b) 1500 (c) 15
  36. 36.Best estimate of 2557 ÷ 36? (a) 640 (b) 6400 (c) 64
  37. 37.Best estimate of 5674 ÷ 73? (a) 8100 (b) 81 (c) 810
  38. 38.Best estimate of 3261 ÷ 36? (a) 8200 (b) 820 (c) 82
  39. 39.Best estimate of 1099 ÷ 81? (a) 14 (b) 140 (c) 1400
  40. 40.Best estimate of 2060 ÷ 36? (a) 5200 (b) 520 (c) 52

Answer key

  1. 7.4
  2. 8.9
  3. 91
  4. 9.9
  5. 23
  6. 32
  7. 9.5
  8. 6.7
  9. 39
  10. 6.3
  11. 15
  12. 66
  13. 88
  14. 60
  15. 78
  16. 83
  17. 8.4
  18. 9.2
  19. 65
  20. 91
  21. 7.9
  22. 15
  23. 9.7
  24. 5.7
  25. 6.2
  26. 82
  27. 21
  28. 46
  29. 56
  30. 5.9
  31. 59
  32. 41
  33. 99
  34. 68
  35. 15
  36. 64
  37. 81
  38. 82
  39. 14
  40. 52

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