Height of frustum = h = 8 cm
Radius of lower circular end = r = 12 cm
Radius of upper circular end = R = 18 cm
Let l = slant height
Slant height = l2 = (R-r)2 + h2 cm
= 36 + 64
= 100
or l = 10 cm
We know, Total surface area of frustum = πr2 + πR2 + π(R + r)l cm2
= π × 122 + π × (18 + 12) × 10 cm2
= 3.14(144 + 324 + 300)
= 2411.52
Total surface area of frustum is 2411.52 cm2