If two conical pieces of wood are cut out from a cylindrical piece of wood from two ends whose radius and height are 7cm and 10cm, then find the total surface area of the remaining part where the radius of the conical part is the same as the radius of the cylinder and the height of the cone is 60% less than the height of the cylindrical part.

If two conical pieces of wood are cut out from a cylindrical piece of wood from two ends whose radius and height are 7cm and 10cm, then find the total surface area of the remaining part where the radius of the conical part is the same as the radius of the cylinder and the height of the cone is 60% less than the height of the cylindrical part. Correct Answer 44 (10 + √65) cm<sup>2</sup>

Given:

The radius and height of cylindrical wood are 7cm and 10cm

The radius of conical part is same as the radius of cylinder

The height of cylinder is 60% less than the height of cylindrical part.

Calculation:

According to question,

Radius of cone = 7cm

And height of cone = 10 × 40% = 4

So, the slant height of cone = √(72 + 42) = √65

Now, the required surface area of the remaining part = 2πr h + 2 × πrl

So, 2 × 22/7 × 7 (10 + √65)

Hence, 44 (10 + √65) cm2

Related Questions

Historically, the production of wood charcoal in locations where there is an abundance of wood dates back to a very ancient period, and generally consists of piling billets of wood on their ends so as to form a conical pile, openings being left at the bottom to admit air, with a central shaft to serve as a flue. The whole pile is covered with turf or moistened clay. The firing is begun at the bottom of the flue, and gradually spreads outwards and upwards. The success of the operation depends upon the rate of the combustion. Under average conditions, 100 parts of wood yield about 60 parts by volume, or 25 parts by weight, of charcoal; small-scale production on the spot often yields only about 50%, while large-scale became efficient to about 90% even by the seventeenth century. The modern process of carbonizing wood, either in small pieces or as sawdust in cast iron retorts, is extensively practiced where wood is scarce, and also for the recovery of valuable byproducts (wood spirit, pyroligneous acid, wood tar), which the process permits. The information given, if accurate, most strongly supports which of the following?