Square Root of a Number

[workingout]

What is your favorite method for finding the square root of a number, to 2 decimal places without a calculator?

I need to try several methods to see which one I like best.

 

[John Benz]

There is no set rule or formula for calculating the square root of a number. In school, they now let the kids use a calculator for homework, but I showed my daughter the only way I know, which is as follows, and I am using a number straight from her algebra homework.

She was told to find the square root of 7,921. I told her to multiply 100 x 100, which I knew was 10,000. We know 7,921 is a little lower and the quotient ends in the number 1. So although I could have told her to multiply 90 x 90 to get 81,000, I explained to her it had to be either 91 or 89 as the the answer had to end in 1. She guessed 89 and got it right. 89 x 89=7921

 

[mrhtbd]

Wow, that was pretty easy. Wish someone had taught me that in high school.

 

[Rocky07]

yeah bro thats about the best way--if its a 2 digit number then start with 10x10--3 digit or 4 digit number then start at 100x100 and so on and so on.

 

[HOTROCKS]

I'll be damned !
Rocky can count ;-)

 

[workingout]

yea that works when the number has a perfect square, but what about a number without a perfect square, like 7,963

 

[Guest]

then ur screwed
lol use a calculator

 

[workingout]

:headshot:

 

[Guest]

all i could say is trial and error but i just picked a not perfect square number and its alot hard then it looks especially without a calculator. all i could suggest is picking a number that is close to the square so if its 85 thats ur number pick 9 cuz 9x9 is 81 then go up by points like 9.2 but it gos into alot more decimals then that i think

 

[basskiller]

There is no set rule or formula for calculating the square root of a number. In school, they now let the kids use a calculator for homework, but I showed my daughter the only way I know, which is as follows, and I am using a number straight from her algebra homework.

She was told to find the square root of 7,921. I told her to multiply 100 x 100, which I knew was 10,000. We know 7,921 is a little lower and the quotient ends in the number 1. So although I could have told her to multiply 90 x 90 to get 80,000, I explained to her it had to be either 91 or 89 as the the answer had to end in 1. She guessed 89 and got it right. 89 x 89=7921

pretty slick.. thanks!! that made it quite easy!!

 

[Rocky07]

when its not a perfect number then wouldnt it make sense to look at the last numeral of the number for instance. 5,689. look at "9". the square root of 9 is 3 if im not mistaken (i know it true lol) so ur first number behind the decimal should be 3. i havent even checked this and it may not be close but its worth a try

 

[Rocky07]

WOW! dont use that method! i just checked it and that is waaaay the f*ck off lol. im leaving this thread for good now lol

 

[John Benz]

yea that works when the number has a perfect square, but what about a number without a perfect square, like 7,963

89.23564 is as close as you can get to a final square root for the number 7,963, and gives the finished quotient of 7,962.999, which is just one thousand short of your number. No two numbers multiplied together can end in 3, so it takes 4-5 tries, starting with 89, and going slightly higher on the decimal each time. If you square 89.2357, you end up with 7,963.01, just one hundredth over your number. The square root of this number is 89.23564310296643, but even most college professors would allow you to round it off at the 100th or 1000th.

 

[John Benz]

when its not a perfect number then wouldnt it make sense to look at the last numeral of the number for instance. 5,689. look at "9". the square root of 9 is 3 if im not mistaken (i know it true lol) so ur first number behind the decimal should be 3. i havent even checked this and it may not be close but its worth a try

I took me 6 tries, but 75.425459 is the precise square root of 5,689.

 

[workingout]

well six tries is not bad, the test will only have one problem on it where I have to square a number, and its not timed. So it should be a slam dunk.

 

[Rocky07]

you'll probably do good on it homie, but seriously--why in the world would u ask a bunch of juice junkies about math lol. if its not counting by 45's or converting grams to mg/cc then the majority of us are probably clueless...but i will take credit for 1 thing--we may not be able to teach u how to do it but i bet we can show you how NOT to do it!

 

[workingout]

if its not counting by 45's or converting grams to mg/cc then the majority of us are probably clueless...

an instant classic. should be the thought of the day. lol

you would be surprised how many smart mofo's are on this board. after all I'm here...