The total surface area of a circular cylinder is 1540sq.cm.If the height is four times the radius of the base , find the height of the cylinder.
Height=4× radius of the base.
⇒h=4r where r is the radius of the base
Total surface area=1540sq.cm
2πr(r+h)=1540
⇒2πr(r+4r)=1540
⇒2×227×5r2=1540
⇒r2=1540×722×10=49
∴r=7
Hence height =h=4r=4×7=28cm