Question

A solid cylinder is of height 15cm and diameter 7cm. Two equal conical holes of radius 3 cm and height 4cm are cut off, one from each circular end. Find the surface area of the remaining solid.

Answer 1

solid=ar. of cylinder+ar. of cone
diameter of cylinder=7cm
radius=7/2cm
radius of conical hole=3cm
height=4cm
so l=h^2+r^2(hole root)
l=(4)^2+(3)^2(hole root)
l=16+9(hole root)
l=25(hole root)
root of 25 is 5 so,
l=5cm
put it in formula,
2*22/7*7/2*15+2(22/7*3*5)   (because there are two conical holes)
330+2(22/7*3*5)
330+2(330/7)
330+660/7
2310+660/7
2970/7cm^2