Arithmetic and rounding

Probability

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Jan 26, 2012
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I can do this all day long using a calculator, but would really like to understand how it is done!

I am working with powers, I have

625 ^ 3/4 = 125

First I bring over the 4 to get;

4 square root (625)^3 = 125

OK from here the problems begin.

square root of (625) = 25, and if I square it I get back to 625, so OK with that.

But how do I work out the 4th root of the square root 625?

Once I have done that I know I will end up with 5^3 = 125

But I just don't know how to work out the 4th square root above?
 
I can do this all day long using a calculator, but would really like to understand how it is done!

I am working with powers, I have

625 ^ 3/4 = 125

First I bring over the 4 to get;

4 square root (625)^3 = 125

OK from here the problems begin.

square root of (625) = 25, and if I square it I get back to 625, so OK with that.

But how do I work out the 4th root of the square root 625?

Once I have done that I know I will end up with 5^3 = 125

But I just don't know how to work out the 4th square root above?

You have not defined your problem! Is your problem:

Prove the following identity:

[625]34 = 125\displaystyle \left [625\right ]^{\frac{3}{4}} \ = \ 125

Or something else....
 
I can do this all day long using a calculator, but would really like to understand how it is done!

I am working with powers, I have

625 ^ 3/4 = 125

First I bring over the 4 to get;

4 square root (625)^3 = 125

OK from here the problems begin.

square root of (625) = 25, and if I square it I get back to 625, so OK with that.

But how do I work out the 4th root of the square root 625?

Once I have done that I know I will end up with 5^3 = 125

But I just don't know how to work out the 4th square root above?
I am not following you at all.

52=25 and 625=252    625=(52)2=54\displaystyle 5^2 = 25\ and\ 625 = 25^2 \implies 625 = \left(5^2\right)^2 = 5^4?

So 625(3/4)=(54)(3/4)=5(43/4)=53=125.\displaystyle 625^{(3/4)} = \left(5^4\right)^{(3/4)} = 5^{(4 * 3 / 4)} = 5^3 = 125.
 
I am not following you at all.

52=25 and 625=252    625=(52)2=54\displaystyle 5^2 = 25\ and\ 625 = 25^2 \implies 625 = \left(5^2\right)^2 = 5^4?

So 625(3/4)=(54)(3/4)=5(43/4)=53=125.\displaystyle 625^{(3/4)} = \left(5^4\right)^{(3/4)} = 5^{(4 * 3 / 4)} = 5^3 = 125.

Thanks Jeff, I've understood your method
 
I can do this all day long using a calculator, but would really like to understand how it is done!

I am working with powers, I have

625 ^ 3/4 = 125

First I bring over the 4 to get;

4 square root (625)^3 = 125

How did you get to the statement above? What does "bring over the 4" mean - why would you do that?

OK from here the problems begin.

square root of (625) = 25, and if I square it I get back to 625, so OK with that.

But how do I work out the 4th root of the square root 625?

Once I have done that I know I will end up with 5^3 = 125

But I just don't know how to work out the 4th square root above?
.
 
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