Find the slant height of a square based right pyramid whose perimeter of the base is 40m and its lateral surface area is 120m2. What is its total surface area?
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Given: P=4a=40m, L.S.A=120m2, we have to find l and T.S.A. Using L.S.A=12Pl, we have 120=12×40×l. This gives l=6m. Thus, slant height=6m. We also have 40=P=4a so that a=10. Hence B=a2=100m2. This gives T.S.A=B+L.S.A=100+120=220m2.