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    Maths question whats the square root of 99 how do i work it out?? please be kind

    Just looking at some maths videos on youtube, and i was messing around with some maths doodling on some paper and what not :), and i was having a little trouble working this one out please if u can help me i would i appreciate it thanx!

    13 Comments

    Answer:
    SQRT(99) is an irrational, approximately equal to 9.95. [I bet you already
    knew that it was just a little less than 10] Here's how I came up with
    9.95 without using a calculator:
    Since 10^2 = 100, SQRT(99) must be 10-d where d is much smaller than 1.
    A little algebra:
    (10-d)*(10-d)=99
    100-20*d+d*d =99
    1-20*d+d*d = 0
    1-20*d = -d*d, but d and for a good approximation, we can assume it's 0:
    1-20*d ~= 0
    ergo d = 1/20 = 0.05
    The actual value of SQRT(99) is 9.94987, so our approximation is pretty
    good.

    9.9498743710662

    Turn calculator on

    Type "99"

    Press square root button

    Done

    trial & error says its somewhere between 9.94 & 9.95.

    Original Poster

    skusey;7842395

    Answer:SQRT(99) is an irrational, approximately equal to 9.95. [I bet you … Answer:SQRT(99) is an irrational, approximately equal to 9.95. [I bet you alreadyknew that it was just a little less than 10] Here's how I came up with9.95 without using a calculator:Since 10^2 = 100, SQRT(99) must be 10-d where d is much smaller than 1.A little algebra: (10-d)*(10-d)=99 100-20*d+d*d =99 1-20*d+d*d = 0 1-20*d = -d*d, but d and for a good approximation, we can assume it's 0: 1-20*d ~= 0 ergo d = 1/20 = 0.05The actual value of SQRT(99) is 9.94987, so our approximation is prettygood.



    :w00t:

    Banned

    ChrisUK;7842409

    Turn calculator onType "99"Press square root buttonDone




    job done!

    dav1d_uk;7842549

    job done!



    +1 ... lol

    Original Poster

    arcangel111;7842604

    +1 ... lol



    - 1 :roll:;-) maths is fun when your not cheating, with a calculator or looking up the answers, on google and then pasting the answers here:-D

    skusey;7842395

    Answer:SQRT(99) is an irrational, approximately equal to 9.95. [I bet you … Answer:SQRT(99) is an irrational, approximately equal to 9.95. [I bet you alreadyknew that it was just a little less than 10] Here's how I came up with9.95 without using a calculator:Since 10^2 = 100, SQRT(99) must be 10-d where d is much smaller than 1.A little algebra: (10-d)*(10-d)=99 100-20*d+d*d =99 1-20*d+d*d = 0 1-20*d = -d*d, but d and for a good approximation, we can assume it's 0: 1-20*d ~= 0 ergo d = 1/20 = 0.05The actual value of SQRT(99) is 9.94987, so our approximation is prettygood.



    Lmao!

    skusey;7842395

    Answer:SQRT(99) is an irrational, approximately equal to 9.95. [I bet you … Answer:SQRT(99) is an irrational, approximately equal to 9.95. [I bet you alreadyknew that it was just a little less than 10] Here's how I came up with9.95 without using a calculator:Since 10^2 = 100, SQRT(99) must be 10-d where d is much smaller than 1.A little algebra: (10-d)*(10-d)=99 100-20*d+d*d =99 1-20*d+d*d = 0 1-20*d = -d*d, but d and for a good approximation, we can assume it's 0: 1-20*d ~= 0 ergo d = 1/20 = 0.05The actual value of SQRT(99) is 9.94987, so our approximation is prettygood.



    Google is far too good

    newton.dep.anl.gov/ask…htm :w00t:

    choc1969;7843142

    Google is far too … Google is far too goodhttp://www.newton.dep.anl.gov/askasci/math99/math99021.htm :w00t:



    LOL.. caught out....well spotted....:thumbsup:

    Iteration :

    We know that 10x10=100 and 9x9=81 so the square root of 99 is definitely between 9 and 10. Hopefully it is apparent that the answer is likely to be closer to 10 than it is 9. In order to find out if the answer is closer to 10 or 9 you would calculate 9.5x9.5 (=90.25) and see if you need a number greater than or less than 9.5. Hopefully you'd be able to see that calculating 9.9x9.9 (=98.01) would be a good idea. You would then need to calculate 9.95x9.95 (=99.025) to see if you need a number greater or less than 99.5. You would keep repeating this method of calculation (iterating) until you reach the desired number of decimal places.

    I hope that explains it :-)

    Your calculations would look like:
    10 * 10 = 100 (too big)
    9 * 9 = 81 (too small)
    9.5 * 9.5 = 90.25 (too small)
    9.9 * 9.9 = 98.01 (too small)
    9.95 * 9.95 = 99.025 (too big)
    9.94 * 9.94 = 98.8036 (too small)
    9.945 * 9.945 = 98.903025 (too small)
    9.949 * 9.949 = 98.982601 (too small)
    9.9495 * 9.495 = 98.9925503 (too small)

    and so on.....

    Banned

    choc1969;7843142

    Google is far too … Google is far too goodhttp://www.newton.dep.anl.gov/askasci/math99/math99021.htm :w00t:



    DEALofaLifetime shame on you lol, good spot choc1969 - the cheek of it.....
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