Answer :
[tex]\frac{2.1X10^8}{4.2X10^2}[/tex]
Since the question requires determining how many times 4.2 x 10^2 will be found in 2.1 x 10^8.
We simply have to divide 2.1 x 10^8 by 4.2 x 10^2
[tex]\frac{2.1}{4.2}\text{ x}\frac{10^8}{10^2}[/tex]Dividing the numerator and denominator and applying the laws of indices
[tex]\frac{1}{2}X10^{8\text{ - 2}}[/tex]=> 0.5 x 10^6
=> 5 x 10^5
Option C is correct