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Estimating Square Roots and Division Worksheet

Mental maths lesson 27: Estimate divisions and square roots · Set 398 · 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.Best estimate of 1984 ÷ 69? (a) 28 (b) 2800 (c) 280
  2. 2.√20 to 1 decimal place? (a) 4.2 (b) 4.5 (c) 4.3 (d) 4.4
  3. 3.Best estimate of 2489 ÷ 54? (a) 50 (b) 500 (c) 5000
  4. 4.Best estimate of 6017 ÷ 72? (a) 86 (b) 860 (c) 8600
  5. 5.Best estimate of 1778 ÷ 72? (a) 250 (b) 25 (c) 2500
  6. 6.√56 to 1 decimal place? (a) 7.8 (b) 7.6 (c) 7.7 (d) 7.5
  7. 7.Best estimate of 2808 ÷ 33? (a) 9400 (b) 94 (c) 940
  8. 8.√82 to 1 decimal place? (a) 9.1 (b) 9.2 (c) 9.3 (d) 9.0
  9. 9.√50 to 1 decimal place? (a) 7.3 (b) 7.2 (c) 7.4 (d) 7.1
  10. 10.Best estimate of 4901 ÷ 73? (a) 700 (b) 70 (c) 7000
  11. 11.Best estimate of 4106 ÷ 76? (a) 51 (b) 5100 (c) 510
  12. 12.Best estimate of 4867 ÷ 52? (a) 97 (b) 9700 (c) 970
  13. 13.Best estimate of 484 ÷ 21? (a) 24 (b) 2400 (c) 240
  14. 14.Best estimate of 7483 ÷ 86? (a) 830 (b) 8300 (c) 83
  15. 15.Best estimate of 3580 ÷ 79? (a) 45 (b) 450 (c) 4500
  16. 16.√83 to 1 decimal place? (a) 9.4 (b) 9.3 (c) 9.2 (d) 9.1
  17. 17.Best estimate of 3704 ÷ 51? (a) 74 (b) 7400 (c) 740
  18. 18.√32 to 1 decimal place? (a) 5.6 (b) 5.5 (c) 5.7 (d) 5.4
  19. 19.Best estimate of 956 ÷ 48? (a) 19 (b) 1900 (c) 190
  20. 20.Best estimate of 1029 ÷ 63? (a) 17 (b) 170 (c) 1700
  21. 21.√75 to 1 decimal place? (a) 8.7 (b) 8.9 (c) 8.6 (d) 8.8
  22. 22.√26 to 1 decimal place? (a) 5.1 (b) 4.9 (c) 4.8 (d) 5.0
  23. 23.Best estimate of 4947 ÷ 73? (a) 7100 (b) 710 (c) 71
  24. 24.Best estimate of 1695 ÷ 29? (a) 570 (b) 57 (c) 5700
  25. 25.Best estimate of 4005 ÷ 51? (a) 800 (b) 80 (c) 8000
  26. 26.Best estimate of 3337 ÷ 72? (a) 480 (b) 4800 (c) 48
  27. 27.Best estimate of 1090 ÷ 76? (a) 1400 (b) 140 (c) 14
  28. 28.√98 to 1 decimal place? (a) 10.0 (b) 10.2 (c) 9.9 (d) 10.1
  29. 29.√46 to 1 decimal place? (a) 7.0 (b) 6.8 (c) 6.7 (d) 6.9
  30. 30.Best estimate of 2299 ÷ 71? (a) 3300 (b) 33 (c) 330
  31. 31.Best estimate of 4018 ÷ 56? (a) 6700 (b) 67 (c) 670
  32. 32.√70 to 1 decimal place? (a) 8.5 (b) 8.7 (c) 8.4 (d) 8.6
  33. 33.Best estimate of 2950 ÷ 31? (a) 9800 (b) 980 (c) 98
  34. 34.√58 to 1 decimal place? (a) 7.6 (b) 7.4 (c) 7.5 (d) 7.3
  35. 35.√55 to 1 decimal place? (a) 7.7 (b) 7.5 (c) 7.6 (d) 7.4
  36. 36.Best estimate of 3204 ÷ 41? (a) 800 (b) 80 (c) 8000
  37. 37.Best estimate of 848 ÷ 48? (a) 170 (b) 1700 (c) 17
  38. 38.Best estimate of 2292 ÷ 83? (a) 290 (b) 2900 (c) 29
  39. 39.√24 to 1 decimal place? (a) 4.7 (b) 4.8 (c) 4.9 (d) 4.6
  40. 40.Best estimate of 3045 ÷ 33? (a) 10200 (b) 102 (c) 1020

Answer key

  1. 28
  2. 4.5
  3. 50
  4. 86
  5. 25
  6. 7.5
  7. 94
  8. 9.1
  9. 7.1
  10. 70
  11. 51
  12. 97
  13. 24
  14. 83
  15. 45
  16. 9.1
  17. 74
  18. 5.7
  19. 19
  20. 17
  21. 8.7
  22. 5.1
  23. 71
  24. 57
  25. 80
  26. 48
  27. 14
  28. 9.9
  29. 6.8
  30. 33
  31. 67
  32. 8.4
  33. 98
  34. 7.6
  35. 7.4
  36. 80
  37. 17
  38. 29
  39. 4.9
  40. 102

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