• Share
  • Email
  • Embed
  • Like
  • Save
  • Private Content
Extracting Cube Roots Mentally
 

Extracting Cube Roots Mentally

on

  • 41,352 views

How do you find cube roots, using only your mind? This slideshow will show you how!

How do you find cube roots, using only your mind? This slideshow will show you how!

Statistics

Views

Total Views
41,352
Views on SlideShare
40,160
Embed Views
1,192

Actions

Likes
5
Downloads
611
Comments
3

39 Embeds 1,192

http://gmmentalgym.blogspot.com 512
http://members.cox.net 133
http://www.slideshare.net 91
http://gmmentalgym.blogspot.com.es 83
http://gmmentalgym.blogspot.co.uk 81
http://gmmentalgym.blogspot.in 67
http://gmmentalgym.blogspot.ca 27
http://gmmentalgym.blogspot.ch 25
http://gmmentalgym.blogspot.com.au 24
http://gmmentalgym.blogspot.fr 18
http://gmmentalgym.blogspot.se 16
http://gmmentalgym.blogspot.de 15
http://gmmentalgym.blogspot.mx 11
http://gmmentalgym.blogspot.com.br 11
http://gmmentalgym.blogspot.no 7
http://gmmentalgym.blogspot.be 7
http://gmmentalgym.blogspot.it 6
http://gmmentalgym.blogspot.gr 5
http://www.mybestcv2.co.il 5
http://gmmentalgym.blogspot.sg 5
http://gmmentalgym.blogspot.co.il 4
http://gmmentalgym.blogspot.nl 4
http://gmmentalgym.blogspot.ie 4
http://gmmentalgym.blogspot.com.ar 4
url_unknown 4
http://gmmentalgym.blogspot.fi 3
http://gmmentalgym.blogspot.ru 3
http://gmmentalgym.blogspot.co.nz 3
http://mentalgym.freehostia.com 2
http://gmmentalgym.blogspot.dk 2
http://learningsglobal.com 2
http://avataros.blogspot.com 1
http://avataros.blogspot.com 1
http://duckduckgo.com 1
http://static.slideshare.net 1
http://gmmentalgym.blogspot.co.at 1
http://translate.googleusercontent.com 1
http://gmmentalgym.blogspot.ae 1
http://headinside.blogspot.com 1
More...

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel

13 of 3 previous next Post a comment

  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
  • its worthy :) nice...
    Are you sure you want to
    Your message goes here
    Processing…
  • I reckon its a reely kool method.
    Are you sure you want to
    Your message goes here
    Processing…
  • Good One.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

    Extracting Cube Roots Mentally Extracting Cube Roots Mentally Presentation Transcript

    • Extracting Cube Roots Mentally
      • Presented by Grey Matters Mental Gym
      • http://members.cox.net/beagenius/
    • Extracting Cube Roots Mentally
      • A cube is a number multiplied by itself twice more. For example, 3 cubed (3 3 ) is 3 * 3 * 3, or 27.
      • A cube root is the number that, when cubed, results in a given number. For example, the cube root of 27 ( 3 √27) is 3.
    • Extracting Cube Roots Mentally
      • Have a spectator choose any number from 1 to 100, cube it with their calculator and give you the answer.
      • Imagine being able to figure the cube root of that number in your head!
    • Extracting Cube Roots Mentally Requirements
      • Calculator
      • Spectator
    • Extracting Cube Roots Mentally
      • To be able to extract cube roots mentally, you must know the first 10 cubes mentally:
      • 1 3 =1 2 3 =8
      • 3 3 =27 4 3 =64
      • 5 3 =125 6 3 =216
      • 7 3 =343 8 3 =512
      • 9 3 =729 10 3 =1000
    • Extracting Cube Roots Mentally
      • Note that no two cubes end in the same digit:
      • 1 3 = 1 2 3 = 8
      • 3 3 =2 7 4 3 =6 4
      • 5 3 =12 5 6 3 =21 6
      • 7 3 =34 3 8 3 =51 2
      • 9 3 =72 9 10 3 =100 0
    • Extracting Cube Roots Mentally
      • Also notice that the cubes of 1, 4, 5, 6, 9 and 0 end in those same digits:
      • 1 3 = 1 2 3 =8
      • 3 3 =27 4 3 =6 4
      • 5 3 =12 5 6 3 =21 6
      • 7 3 =343 8 3 =512
      • 9 3 =72 9 10 3 =100 0
    • Extracting Cube Roots Mentally
      • Finally, notice that 2 3 ends in 8, 8 3 ends in 2, 3 3 ends in 7 and 7 3 ends in 3:
      • 1 3 =1 2 3 = 8
      • 3 3 =2 7 4 3 =64
      • 5 3 =125 6 3 =216
      • 7 3 =34 3 8 3 =51 2
      • 9 3 =729 10 3 =1000
    • Extracting Cube Roots Mentally
      • If you’re given one of the cubes you’ve memorized from this chart, simply give the cube root you’ve remembered.
    • Extracting Cube Roots Mentally
      • If you’re given a number that ranges from 1,000 (10 3 ) to 1,000,000 (100 3 ), you’ll need to go through the following steps.
    • Extracting Cube Roots Mentally
      • First, split the number into two parts at the comma. As an example, let’s say you’re given the number 39,304. You would mentally split it into “39” and “304”.
    • Extracting Cube Roots Mentally
      • Next, focusing on the number to the left of the comma, ask yourself, “What is the largest cube that is equal to or less than that number?”
      • In our example, the largest cube that is equal to or less than 39 (the number to the left of the comma) is 27.
    • Extracting Cube Roots Mentally
      • Recall the cube root of this number, and that will be the tens digit of the answer.
      • In our example, we found that 27 was the largest cube less than or equal to 39. Since we know that the cube root of 27 is 3 ( 3 √27=3), we now know our answer is in the 30s somewhere.
    • Extracting Cube Roots Mentally
      • Now, focus on the number to the right of the comma. In our example of 39,304, this would be the “304”.
    • Extracting Cube Roots Mentally
      • Look at just the rightmost digit, and ask yourself, “Which digit, from 0-9, when cubed, would result in that digit?” This will be the ones digit of the answer.
      • In our example of 39,304, we see that the rightmost digit is a 4. Remembering that 4 is the only cube that ends in a 4 (4 3 =64), this must be the ones digit of the answer!
    • Extracting Cube Roots Mentally
      • Once you know both the tens digit and the ones digit of the answer, put them together and you have the cube root.
      • In our example, we determined that the answer for “39,304” is in the 30s, and that it ends in 4, so we give 34 as the cube root!
    • Extracting Cube Roots Mentally
      • Other examples:
      • What is 3 √50,653? Because “50” is greater than 27 (3 3 ), and less than 64 (4 3 ), we know the answer is in the 30s. Because “653” ends in 3, we know that the answer must end in 7, as only 7 3 (343) ends in 3. Therefore, 3 √50,653=37.
    • Extracting Cube Roots Mentally
      • Other examples:
      • What is 3 √314,432? Because “314” is greater than 216 (6 3 ), and less than 343 (7 3 ), we know the answer is in the 60s. Because “432” ends in 2, we know that the answer must end in 8, as only 8 3 (512) ends in 2. Therefore, 3 √314,432=68.
    • Extracting Cube Roots Mentally
      • Other examples:
      • What is 3 √704969? Because “704” is greater than 512 (8 3 ), and less than 729(9 3 ), we know the answer is in the 80s. Because “969” ends in 9, we know that the answer must end in 9, as only 9 3 (729) ends in 9. Therefore, 3 √704969=89.