question_answer

If the \[\Delta \] ABC is right angled at B, the circum radius of the sides AB and BC are 15 cm and 20 cm respectively is

A)  17.2cm                        

B)  12.7cm

C)  12.5cm                        

D)  15.2cm

Correct Answer: C

Solution :

           OA = OC = circum-radius \[\angle B\text{ }=90{}^\circ \] \[\therefore \text{ }A{{C}^{2}}=A{{B}^{2}}+B{{C}^{2}}={{15}^{2}}+{{20}^{2}}\] \[=225+400=625\] \[\therefore \]\[AC=\sqrt{625}=25\] cm \[\therefore \]\[OA=25\div 2=12.5\]cm