It was decided to put 20 street lights on a lonely road in order to secure the area at night - Maths - Surface Areas and Volumes

Question

It was decided to put 20 street lights on a lonely road in order to
secure the area at night each light was in the shape of a right
circular cone mounted on a right circular cylinder having base
radius 40 cm height of cylindrical part is 45 cm and that of
conical part is 30 cm find the surface area of a street light and
if it costs rs 15 per 100 cm2 , what will be the cost to
install 20 such lights?

Anuradha Sharma · Accepted Answer

Dear Student,

Please find below the solution to the asked query :
CSA of one street light = CSA of cone+CSA of cylinder= πrl+2πrH=πrr2+h2+2πrH       where h is the height of cone and H is the height of cylinder= 3
14×40×402+302+2×3
14×40×45=17584 cm2Now Surface area of all street lights = 20×17584= 351680 cm2Now cost of such 20 lights = 15100×351680=Rs
 52752

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