1. From a point Q, the length of the tangent to a circle is 24 cm and the distance of Q from the centre is 25 cm. The radius of the circle is
(A) 7 cm
(B) 12 cm
(C) 15 cm
(D) 24.5 cm
The correct option is (A) = 7 cm
Given that,
The length of the tangent (QT) is 24 cm and the length of OQ is 25 cm .
Suppose the length of the radius OT is $l \mathrm{~cm}$.
We know that $\triangle O T Q$ is a right-angle triangle. So, by using Pythagoras theorem-
$O Q^2=T Q^2+O T^2$
$l=\sqrt{25^2-24^2}$
$O T=l=\sqrt{49}$
$\text { OT }=7 \mathrm{~cm}$