EXERCISE 25 A
1. Find the surface area of each of the cuboids whose dimensions are given below
| (i) | (ii) | (iii) | (iv) | (v) | |
| l | 9 cm | 5 cm | 12 cm | 5 cm | $5\dfrac{1}{2}$ |
| b | 4 cm | 5 cm | 10 cm | 1.5 cm | 4cm |
| h | 3 cm | 10 cm | 4 cm | 2.4 cm | $10\dfrac{1}{2}$ |
2. Find the surface area of the following cubes.
(i) l = 8 cm
(ii) l = 12 cm
(iii) $l=\dfrac{1}{2}~m$
(iv) l = 5 dm
3. The total surface area of cube is 96 cm2 . what is the length of its sides ?
4. The total surface of a wooden box which is in the shape of a cube . If the edge of the box is 25 cm.
5. Find the cost of painting all round the outer surface of a box with lid 100 cm long , 80 cm wide and 60 cm high at 2 rupees per 40 cm2
6. The dimensions of an oil can are 26 cm × 26 cm × 45 cm . Find the area of the tin sheet required for making 20 such cans . If 1 sq m of the tin sheet costs 10 rupees , find the cost of tin used for these 20 cans .
7. Find the area of the four walls with following measurements
(i) Length = 8 m , width = 6 m and height = 4 cm
(ii) Length = 10 m , width = 7 m and height = 5 m
8. (i) A rectangular room is 6 m long, 5 m wide and 4 m high. Find the total surface area of the four walls .
(ii) If the windows and door in the above room are made up of 20% of the wall area , how much paint will be needed to give the four walls (excluding the windows and door) two coats of paint if a litre of paint is used to cover 18 m2 in one coat .
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