Question

Question #9f1a5

Answer 1

`~~4.582`

Explanation:

To estimate you will need to d a lot of multiplication of squares by hand:

You know `sqrt(16) = 4` and `sqrt(25) = 5`

This means the `sqrt(21)` is in between. Since `21` is about half way between `16` and `25` select the decimal `4.5` and square it.

`4.5^2 = 20.25` so we know we are getting close.

Try `4.55^2 = 20.7025` which is smaller so we need a higher decimal value.

Try `4.57^2 = 20.8849` which is smaller so we need a higher decimal value.

Try `4.58^2 = 20.9764` Hope this is close enough. If not, try `4.582^2 = 20.994724`