# How do you use a calculator to evaluate the expression log5 to four decimal places?

Jan 31, 2017

$0.698970004 \rightarrow 0.6990$

#### Explanation:

As there is no base shown, it is assumed that the base is 10.

Calculators have a key: LOG

If you have a D.A.L. calculator the key presses are as follows:

LOG 5 =

The display will be $0.698970004$

The older calculators require the 5 to be entered first and then LOG.
The answer is displayed immediately without =being pressed.

5 LOG

The display will be $0.698970004$

To round to 4 decimal places, consider the value in the fifth place.

$0.6989 \textcolor{b l u e}{7} 0004$

$7$ is more than 5, so the digit to the left will round up.
The $9$ becomes 10, meaning the $8$ will become $9$.
$\left(89 \rightarrow 90\right)$

$0.698 \textcolor{red}{9} 70004$ rounds to

$0.6990$

The final $0$ must be shown otherwise there will not be 4 places.