Question 7 Two cones with same base radius 8 cm and height 15 cm are joined together along their bases. Find the surface area of the shape so formed.
If two cones with same base and height are joined together along their bases. Then the shape so formed is look like as figure shown.
Given: Radius of cone, r = 8cm and Height of cone, h = 15 cm
So, Surface area of the shape so formed = Curved area of first cone + Curved surface area of second cone = 2.(Surface area of cone) [Since , both cones are identical] =2×πrl=2×π×r×√r2+h2(l=√r2+h2)=2×227×8×√(8)2+(15)2=2×22×8×√64+2257=44×8×√2897=59847=854.85cm2=855cm2(approx) Hence , the surface area of shape so formed is 855cm2