Advertisement

### Question

A gun is fired towards a circular board consisting of two concentric circles of radii 12 and 3 cm. If each bullet is able to hit the board, what is the probability that it will strike the ring, i.e., the area between the inner and outer circles?

**A**

${15/16}$.

**B**

${5/7}$.

**C**

1/2.

**D**

${15/31}$.

**Soln.**

**Ans: a**

The area of the ring is equal to the difference of the areas of the two circles. π($12^2 - 3^2$) = 135π sq. cm. The total area is π × 12^{2} = 144π. The probability of hitting the ring is ${135π}/{144π}$ = ${15/16}$.