# Which number has one significant figure: 4xx10^(-23) or 4.0xx10^(-23)?

Sep 19, 2015

It would be $4 \times {10}^{- 23}$. $4.0 \times {10}^{- 23}$ would have two sig figs.

Sep 19, 2015

the correct answer is $4 \times {10}^{- 23}$

#### Explanation:

$4 \times {10}^{- 23}$ is one significant figure.

$4.0 \times {10}^{- 23}$ is two significant figures since it contains a trailing zero in a number that has a decimal point.

Here is a full explanation on significant figures:

Source: Screenshot from my teaching notes.