# CBSE Class 10-Mathematics: Chapter – 13 Surface Areas and Volumes Part 10 (For CBSE, ICSE, IAS, NET, NRA 2022)

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**Question 13**:

A container, opened from the top and made up of a metal sheet, is in the form of a frustum of a cone of height with radii of its lower and upper ends as and respectively. Find the total cost of milk which can completely fill the container at the rate of per liter. Also find the cost of metal sheet used to make the container, if it costs per .

**Answer**:

Here,

Cost of the milk

Now, surface area

Area of the metal sheet used

**Question 14**:

A copper wire, in diameter is wound about a cylinder whose length is and diameter , so as to cover the curved surface of the cylinder. Find the length and mass of the wire, assuming the density of copper to .

**Answer**:

Abbreviation: CSA = Curved Surface Area

TSA = Total Surface Area

V = Volume Number of rounds to cover , i.e..

Here, Diameter , Radius

Length of the wire in completing one round

Length of the wire in completing rounds .

Radius of the copper wire

Volume of wire

**Question 15**:

A right triangle, whose sides are and (other than hypotenuse) is made to revolve about its hypotenuse. Find the volume and surface area of the double cone so formed. (Choose value of as found appropriate)

**Answer**:

Hypotenuse

In figure, [AA similarity]

Also,

Volume of the double cone

Surface area of the double cone