Question

what is 0.000345 expressed in scientific notation?
3.45×10²
3.45×10⁴
3.45×10⁻²
3.45×10⁻⁴

Explanation:

Step1: Recall scientific - notation form

Scientific notation is $a\times10^{n}$, where $1\leqslant|a|\lt10$ and $n$ is an integer.

Step2: Move the decimal point

For the number $0.000345$, move the decimal point 4 places to the right to get $a = 3.45$.
Since we moved the decimal point 4 places to the right, $n=-4$. So, $0.000345 = 3.45\times10^{-4}$.

Answer:

D. $3.45\times 10^{-4}$