Answer
FALSE.
Work Step by Step
According to the definition of Scientific Notation given in the textbook, a number is written in scientific notation when it is expressed in the form $a \times 10^n$. $a$ can take any value between $-10$ and $10$, excluding $0$, while $n$ should be an integer and can take any integer value.
In the given case, $a=40$ and $n=2$. While the value of $n$ fulfills the conditions, the absolute value of $a$ is greater than $10$ and does not fulfill the conditions.
The proper Scientific Notation for $40\times10^2$ would be $(4\times10)\times10^2=4\times10^{1+2}=4\times10^3$.