Question

Which of the following option is equal to $r\times r\times r\times r?$

• A. $4r$
• B. $r^4$
• C. $4+r$
• D. $4^r$

Answer 1

The correct option is B $r^4$

$\underset{–}{\text{Concept Involved:}}$
Multiplication of a number to itself $m$ times, such as $a\times a\times a\times ...$ upto $\underset{–}{m}$ times, would be equal to $\underset{–}{a^{(1+1+1+...m\text{times})}=a^m}.$

(multiplication rule of exponents)

Here, $r\times r\times r\times r$ is the multiplication of $r$ to itself $4$ times.
$\therefore r\times r\times r\times r=r^{(1+1+1+1)}=r^4$

Hence, option (b.) is the correct one.