question_answer

The height of a conical tent at the centre is 5 r The distance of any point on its circular base from the top of the tent is 13 m. The area of the slant surface is

A)  144 \[\pi \] sq m       

B)         130 \[\pi \] sq m

C)  156 \[\pi \] sq m         

D)         169 \[\pi \] sq m

Correct Answer: C

Solution :

 Given, \[h=5m,\,\,l=13m.\] Let r is radius of the base.       Hence, from \[\Delta \,\,PQC,\]                                 \[{{13}^{2}}={{5}^{2}}+{{r}^{2}}\] or            \[{{r}^{2}}=169-25=144\] or            \[r=12\,m\] Hence, area of slant surface \[=\pi \,\,r\,l\]                 \[=\pi \times 12\times 13=156\,\pi \,\,sq.m\].