How do you write $45$ in scientific notation?

Hint: As we know that scientific expression is a method of expressing numbers that are too big or too small to be easily written in decimal form. The general form of writing numbers in scientific notation or scientific form is $N \times {10^m}$ where $N$ is the number between $1$ and $10$, but not $10$ itself, and $m$is any integer whether it is positive or negative integer.

Complete step-by-step solution:
As per the given question, we need to express the given number in scientific notation and we are provided with the number $45$.
We will use the general term to convert it into scientific form, Here $45$ is a whole number so we will move the decimal point to the end of the number one time . It gives us $N = 4.5$.
Here we have moved the decimal one time and because we moved the decimal left, the exponent is positive . Therefore $m = 1$, so we get ${10^1}$.
Now by substituting the value of $N$ and $m$ in the general form of the scientific notation we get: $N \times {10^m} = 4.5 \times {10^1}$.
Hence the scientific notation of $45$ is $4.5 \times {10^1}$.

Note: We should keep these points in mind while solving for scientific notation. These are: the positions of the decimal point should be such that there is only a single digit before it. While moving the decimal points we should take care of the position which has been moved since it determines the power of $10$. Also the direction to which the decimal point is moved we have to note that, it is has been moved to the left then the power is positive and it is moved to the right then the power is negative.