A drain cover is made from a square metal plate of side 40cm having 441 holes of diameter 1cm each drilled in it. Find the area of the remaining square plate.

Explanation

Area of square metal plate `= 40 ×40 cm^2=1600 cm^2`

Area of each hole `= pi r^2=22/7​×(21​)^2 cm^2=11/14 ​cm^2`

∴ Area of 441 holes `= 441 ×11/14​ cm^2=346.5 cm^2`

Hence , Area of the remaining square plate `=(1600−346.5) cm^2=1253.5 cm^2`.