Question

which of the following numbers is written in scientific notation? 20×10^6 1.75×10^6 20 1.31

a. 1.75×10^6
b. 20×10^6
c. 1.31
d. 20

Explanation:

Step1: Recall scientific - notation form

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

Step2: Analyze option A

For $1.75\times 10^{6}$, $a = 1.75$ (where $1\leq1.75\lt10$) and $n = 6$ (an integer), so it is in scientific notation.

Step3: Analyze option B

For $20\times 10^{6}$, $a = 20$ which is not in the range $1\leq|a|\lt10$. It should be rewritten as $2\times10^{7}$ to be in scientific - notation.

Step4: Analyze option C

For $1.31$, it can be written as $1.31\times10^{0}$, but the standard scientific - notation for a number between 1 and 10 is just the number itself without the $10^{0}$ part. It is not in the typical scientific - notation form for non - power - of - 10 numbers.

Step5: Analyze option D

For 20, it can be written as $2\times10^{1}$, but as it is, 20 is not in scientific notation.

Answer:

A. $1.75\times 10^{6}$