Advertisements
Advertisements
प्रश्न
The frustum shaped outer portion of the table lamp has to be painted including the top part. Find the total cost of painting the lamp if the cost of painting 1 sq.cm is ₹ 2.
Advertisements
उत्तर
Slant height of the frustum (l)
= `sqrt("h"^2 + ("R" - "r")^2`
= `sqrt(8^2 + (12 - 6)^2`
= `sqrt(64 + (6)^2`
= `sqrt(64 + 36)`
= `sqrt(100)`
Slant height = 10 m
Total Area to be painted = C.S.A of the Frustum + top area
= πl (R + r) + πr2 sq.units
= π[l (R + r) + r2]
= `22/7[10(12 + 6) + 6^2]`
= `22/7[10 xx 18 + 36] "cm"^2`
= `22/7[180 + 36] "cm"^2`
= `(22 xx 216)/7`
= `4752/7 "cm"^2`
= 678.86 cm2
Cost of painting = ₹ 678.86 × 2 = ₹ 1357.72
APPEARS IN
संबंधित प्रश्न
A metal container, open from the top, is in the shape of a frustum of a cone of height 21 cm with radii of its lower and upper circular ends as 8 cm and 20 cm respectively. Find the cost of milk which can completely fill the container at the rate of Rs 35 per litre.\[\left[ Use \pi = \frac{22}{7} \right]\]
A bucket is in the form of a frustum of a cone and holds 15.25 litres of water. The diameters of the top and bottom are 25 cm and 20 cm respectively. Find its height and area of tin used in its construction.
A cone of radius 4 cm is divided into two parts by drawing a plane through the mid point of its axis and parallel to its base . Compare the volumes of two parts.
A bucket is in the form of a frustum of a cone and holds 28.490 litres of water . The radii of the top and bottom are 28 cm and 21 cm respectively . Find the height of the bucket .
A reservoir is in the shape of a frustum of a right circular cone. It is 8 m across at the top and 4 m across at the bottom. If it is 6 m deep, then its capacity is
A cylinder with base radius of 8 cm and height of 2 cm is melted to form a cone of height 6 cm. The radius of the cone is
A hollow sphere of internal and external diameters 4 cm and 8 cm respectively is melted into a cone of base diameter 8 cm. The height of the cone is
A fez, the cap used by the Turks, is shaped like the frustum of a cone. If its radius on the open side is 10 cm, radius at the upper base is
4 cm and its slant height is 15 cm, then find the area of material used for making it. `["Use" π = 22/7.]`
A milk container is made of metal sheet in the shape of frustum of a cone whose volume is `"10459" 3/7 "cm"^3`. The radii of its lower and upper circular ends are 8 cm and 20 cm, respectively. Find the cost of metal sheet used in making the container at the rate of ₹ 1.40 per cm2.
The slant height of the frustum of a cone having radii of two ends as 5 cm and 2 cm respectively and height 4 cm is ______.
