UPSC CDS 2 2021 Math Paper

Given, dimension of the frustum are :
radius of one circular part, r1=42cm
radius of another circular part, r2=105cm
Vertical height, h=16cm
In △ABC,
(AC)2=AB2+BC2⇒I2=h2+(r2−r1)2
I2=(16)2+(105−42)2‌‌=256+(63)2=256+3969=4225
‌I=√4225=65cm
Hence, the slant height is 65cm.