Express the numbers in scientific notation and state how many significant figures are in the number
1) 0.0020
2) 0.0007
3) 0.000070

Question

Express the numbers in scientific notation and state how many significant figures are in the number
1) 0.0020
2) 0.0007
3) 0.000070

abb0t · Answer

You always add a $\huge 10^{\pm n}$ where $n$ is the number of times you move the decimal. 
For example, if you move the decimal to the $\sf \color{red}{right}$, $n$ would be negative. If you move the decimal to the $\sf \color{blue}{left}$, it would be positive "n".

For all of these, they would be negative "n". The first one is $\sf 2.0 \times 10^{-3}$
You always want to keep the correct number of significant figures. In this case, you have two significant figures, so you keep two. 

Can you try the other two?