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Question:

Find the total surface area of a cone, if its slant height is 21m and diameter of its base is 24m.

Solution:

Given: R = 24/2 = 12m, Slant height = 21m
∴Total Surface area of cone = πr(r+l) = 22/7 × 12(12+21)m² = 22/7 × 12 × 33m² = 1244.57m²