Answer
$\dfrac{1}{49}=2.04 \%$
Work Step by Step
The area is: $ \text{area of a smallest circle} =\pi \times (1)^2=\pi \ cm^2$
Now, the total area is equal to the area of the largest circle $= \pi (7)^2=49 \pi \ cm^2$
The probability that the dart hits the center region is the ratio of area of the center region to the total area:
P(dart hits the center region)$=\dfrac{ \pi}{49 \pi}=\dfrac{1}{49}=2.04 \%$
