Question

Which number is written in scientific notation?

• A. $4.5\times {10}^{-3}$
• B. $14.5\times {10}^2$
• C. $0.78\times {10}^{-6}$
• D. $5.7\times 4^8$

Answer 1

The correct option is A

$4.5\times {10}^{-3}$

Explanation for the correct answer.

Scientific notation is defined by $k\times {10}^n$, where $1\le k\le 9$ and $n$is any integer.

Option (A):

On comparing $4.5\times {10}^{-3}$ with $k\times {10}^n$, we get $k=4.5$ which lies between $1\le 4.5\le 9$ and $n=-3$ is an integer.

Hence, option (A) is correct.

Explanation for incorrect answer.

Option (B):

On comparing $14.5\times {10}^2$ with $k\times {10}^n$, we get $k=14.5$ which is $9<14.5$ and does not lies between $1\le k\le 9$.

Hence, option (B) is incorrect.

Option (C):

On comparing $0.78\times {10}^{-6}$ with $k\times {10}^n$, we get $k=0.78$ which is $0.78<1$ and does not lies between $1\le k\le 9$ .

Hence, option (C) is incorrect.

Option (D):

On comparing $5.7\times 4^8$ with $k\times {10}^n$, we get $k=5.7$ which lies between $1\le k\le 9$ and $n=8$ is an integer but $4\ne 10$.

Hence, option (D) is incorrect.

Hence, option (A) is correct answer.