# Finding a cube root of a number without using calculator .

1. Apr 27, 2015

### Emmanuel_Euler

HI EVERYONE
I was thinking if we could find a cube root without using a calculator.
square root was easy to find without calculator,but cube root i have no idea to find it.
any help??
for example(cube root of 3 or 2)

2. Apr 27, 2015

### Emmanuel_Euler

finding a square root without using calculator.

3. Apr 27, 2015

### Staff: Mentor

You might find it interesting that when I was in the 8th or 9th grade, we were taught how to calculate square roots by the method shown in the video you posted. That was before calculators were invented...

4. Apr 28, 2015

### Svein

A numerical recipe for calculating $\sqrt[3]{a}$. Set $x_{1}=\frac{a}{3}$ and recursively calculate $x_{n+1}=\frac{1}{3}(2x_{n}+\frac{a}{x_{n}^{2}})$. Stop when |xn+1 - xn| is "small enough".

5. Apr 28, 2015

### Emmanuel_Euler

Thank you so much for help.