## Chapter 25 - Surface Areas and Volume of Solids Exercise Ex. 25.1

Question 1
The volume of a cube is 1331 cm3. Find its total surface area.
Solution 1
Question 2
The total surface area of a cube is 864 cm2. Find its volume.
Solution 2

Question 3
The length, breadth, and height of a rectangular solid are in the ratio 6 : 4 :3. If the total surface area is 1728 cm2. Find its dimensions.
Solution 3

Question 4
The length and breadth of a cuboid are 20 cm and 15 cm respectively. If its volume is 2400 cm3, find its height.
Solution 4

Volume of a cuboid = l x b x h
---------------------2400 = 20 × 15 × h
---------------------------h = 8 cm
Hence, height of the cuboid is 8 cm.
Question 5
A square plate of side 'x' cm is 4 mm thick. If its volume is 1440 cm3; find the value of 'x'.
Solution 5
Volume of the square plate = Volume of a cuboid

Question 6
The square on the diagonal of a cube has an area of 441 cm2. Find the length of the side and total surface area of the cube.

Solution 6

Question 7
Three equal cubes are placed adjacently in a row. Find the ratio of the total surface area of the resulting cuboid to that of the sum of the total surface areas of the three cubes.
Solution 7
Question 8
A metal cube of side 4 cm is immersed in a water tank. The length and breadth of the tank are 8 cm and 4 cm respectively. Find the rise in level of the water.
Solution 8
Question 9
A metal piece 6 cm long, 5 cm broad and x cm , high is dropped in a glass box containing water. The dimensions of the base of the glass box are 18 cm by 8 cm and the rise in water level is 0.5 cm. Find x.
Solution 9

Question 10
A closed box is made of wood 5 mm thick. The external length, breadth and height of the box are 21 cm, 13 cm and 11 cm respectively. Find the volume of the wood used in making the box.
Solution 10

Question 11
The cost of papering the four walls of a room at Rs 1 per m2 is Rs. 210. The height of the room is 5 m. Find the length and the breadth of the room if they are in the ratio 5:2.
Solution 11

Question 12
Find the volume of wood used in making a closed box 22 cm by 18 cm by 14 cm, using a 1 cm thick wood. Also, find the cost of wood required to make the box at the rate of Rs. 5 per cm³ How many cubes of side 2 cm can be placed in the box?
Solution 12
Question 13
A rectangular container has base with dimensions 6 cm x 9 cm. A cube of edge 3 cm is placed in the container and then sufficient water is filled into it so that the cube is just submerged. Find the fall in the level of the water in the container, when the cube is removed.
Solution 13

Question 14
The base of a rectangular container is a square of side 12 cm. This container holds water up to 2 cm from the top. When a cube is placed in the water and is completely submerged, the water rises to the top and 224 cm3 of water overflows. Find the volume and surface area of the cube.
Solution 14
Question 15
Solution 15
Question 16
Solution 16
Question 17
Solution 17
Question 18
Solution 18
Question 19
Solution 19

Question 20
Solution 20
Question 21
Solution 21
Question 22
Solution 22
Question 23
Solution 23
Question 24
Solution 24
Question 25
Solution 25
Question 26
Solution 26

Question 27
Solution 27

Question 28
Solution 28
Question 29
Solution 29

Question 30
Solution 30

## Chapter 25 - Surface Areas and Volume of Solids Exercise Ex. 25.2

Question 1
Find the length of 22 kg copper wire of diameter 0.8 cm, if the weight of 1 cm3 copper is 4.2 g.
Solution 1
Question 2
Find the length of a solid cylinder of diameter 4 cm when recast into a hollow cylinder of outer diameter 10 cm, thickness 0.25 cm and length 21 cm? Give your answer correct to two decimal places.
Solution 2
Question 3
A hollow garden roller, 1 m wide with outside diameter of 30 cm, is made of 2 cm thick iron. Find the volume of the iron. If the roller rolls without sliding for 6 seconds at the rate of 8 complete rounds per second, find the distance travelled and the area covered by the roller in 6 seconds.
Solution 3
Question 4
A well with 6 m diameter is dug. The earth taken out of it is spread uniformly all around it to a width of 2 m to form an embankment of height 2.25 m. Find the depth of the well.
Solution 4
Question 5
A cylindrical container with internal diameter of its base 20 cm, contains water upto a height of 14 cm. Find the area of the wet surface of the cylinder.
Solution 5

Question 6
The radius of a solid cylinder decreases by 10% and its height increases by 20%. Find the change in percentage of its volume and curved surface area
Solution 6

Question 7
From a tap of inner radius 0.80 cm, water flows at the rate of 7 m/s. Find the volume in litres of water delivered by the pipe in 75 minutes.
Solution 7

Question 8
A cylindrical water tank has a diameter 4 m and is 6 m high. Water is flowing into it from a cylindrical pipe of diameter 4 cm at the rate of 10 m/s. In how much time the tank will be filled?
Solution 8
Question 9
The difference between the outer and inner curved surface area of a hollow cylinder is 264 cm2. If its height is 14 cm and the volume of the material in it is 1980 cm3, find its total surface area.
Solution 9
Question 10
The sum of the height and the radius of a cylinder is 28 cm and its total surface area is 616 cm2, find the volume of the cylinder.
Solution 10
Question 11
A cylindrical tube, open at both ends, is made of metal. The bore (internal diameter) of the tube is 10.4 cm and its length is 25 cm. The thickness of the metal is 8 mm everywhere. Calculate the volume of the metal. Also, find the weight of the tube if 1 cm3 of the metal weighs 1.42 g.
Solution 11
Question 12
Solution 12

Question 13
Solution 13
Question 14
Solution 14
Question 15
Solution 15
Question 16
Solution 16
Question 17
Solution 17
Question 18
Solution 18
Question 19
Solution 19
Question 20
Solution 20
Question 21
Solution 21
Question 22
Solution 22

Question 23
Solution 23

Question 24
Solution 24
Question 25
Solution 25
Question 26
Solution 26
Question 27
Solution 27

## Chapter 25 - Surface Areas and Volume of Solids Exercise Ex. 25.3

Question 1
The cross section of a piece of metal 2 m in length
is shown.
(a) Calculate the area of cross section.
(b) Calculate the volume of the piece of metal.

Solution 1

Question 2
The figure represents the cross section of a swimming pool 10 m broad, 2 m deep at one end, 3 m deep at the other end. Calculate the volume of water it will hold when full, given that its length is 40 m.

Solution 2
Question 3
The given figure is a cross -section of a victory stand used in sports. All measurements are in centimetres. Assume all angles in the figure are right angles. If the width of the stand is 60 cm, find
(a) The space it occupies in cm3.
(b) The total surface area in m2.

Solution 3

Question 4
Water flows at the rate of 1.5 meters per second through a pipe with area of cross section 2.5 cm2 into a rectangular water tank of length 90 cm and breadth 50 cm. Find the rise in water level in the tank after 4 minutes.
Solution 4
Question 5
A swimming pool is 50 m long and 15 m wide. Its shallow and deep ends are 1.5 m and 4.5 m respectively. If the bottom of the pool slopes uniformly, find the amount of water in kilolitres required to fill the pool (1 m3 = 1000 liters).
Solution 5

Question 6
Rain falls on a rectangular roof 28 m by 9 m and the water flows into a tank of dimensions 90 m by 70 cm by 84 cm. How much rainfall will fill the tank completely?
Solution 6
Question 7
The area of cross section of a pipe is 5.4 square cm and water is pumped out of it at the rate of 27 km per hour. Find, in litres, the volume of water which flows out of the pipe in 2 minutes.
Solution 7
Question 8
The figure shows the cross section of 0.2 m a concrete wall to be constructed. It is 0.2 m wide at the top, 2.0 m wide at the bottom and its height is 4.0 m, and its length is 40 m.

(a) Calculate the cross sectional area
(b) Calculate the volume of the concrete in the wall
(c) If the whole wall is to be painted, find the cost of painting it at 2.50 per sq m.

Solution 8

Question 9
The cross section of a tunnel perpendicular to its length is a trapezium ABCD as shown in the figure. AM = BN; AB = 4.4 m, CD = 3 m The height of a tunnel is 2.4 m. The tunnel is 5.4 m long.

(a) Calculate the cost of painting the internal surface of the tunnel (excluding the floor) at the rate of Rs. 5 per m2.
(b) Calculate the cost of flooring at the rate of Rs.2. 5 per m2.

Solution 9
Question 10
ABCDE is the end view of a factory shed which is 50 m long. The roofing of the shed consists of asbestos sheets as shown in the figure. The two ends of the shed are completely closed by brick walls.

(a) Calculate the total volume content of the shed.
(b) If the cost of asbestos sheet roofing is Rs. 20 per m2, find the cost of roofing.
(c) Find the total surface area (including roofing) of the shed.
Solution 10
Question 11
The cross section of a swimming pool is a trapezium whose shallow and deep ends are 1 m and 3 m respectively. If the length of the pool is 50 m and its width is 1.5 m, calculate the volume of water it holds.
Solution 11
Question 12
A hose-pipe of cross section area 3 cm2 delivers 1800 liters of water in 10 minutes. Find the speed of water in km/h through the pipe.
Solution 12
Question 13
The cross section of a canal is a trapezium with the base length of 3 m and the top length of 5 m. It is 2 m deep and 400 m long. Calculate the volume of water it holds.
Solution 13

Question 14
A rectangular water tank measuring 8mx6mx 4 cm is filled from a pipe of cross sectional area 1.5 cm2, the water emerging at 10 m/s. How long does it take to fill the tank?
Solution 14

Question 15
How many liters of water will flow out of a pipe having a cross sectional area 6 cm2 in one hour, if the speed of water in the pipe is 30 cm/sec?
Solution 15