How many numbers are written in scientific notation?
- $\sqrt7\times10^{-20}$
- $5.3\times2^{10}$
- $(\frac13)^{-1}\times10^{15}$
$1)\text{zero}\qquad\qquad2)1\qquad\qquad3)2\qquad\qquad4)3$
We know that in base $10$ the scientific notation of a number is in the form $c\times10^n$ where $c$ is a number between $1$ and $10$ (not including $10$) and $n\in\mathbb{Z}$. Hence the second number ($5.3\times2^{10}$) is excluded. the third number is the same as $3\times10^{15}$ and I think it is written in scientific notation but for the first one I have doubts because although $\sqrt7\in[1,10)$ but haven't' seen this form of number as a scientific notation before.