Volume and Surface Area

Q.1.Find the surface area of a 10cm*4cm*3cm brick.
A. 154 cm square
B. 156 cm square
C. 160 cm square
D. 164 cm square

Answer: Option D

Explanation: 
Surface area of a cuboid = 2(lb+bh+hl) cm square
So,
Surface area of a brick = 2(10*4+4*3+3*10) cm square
= 2(82) cm square = 164 cm square

Q.2. A cistern 6 m long and 4 m wide contains water up to a breadth of 1 m 25 cm. Find the total area of the wet surface.
A. 42 m sqaure
B. 49 m sqaure
C. 52 m sqaure
D. 64 m sqaure

Answer: Option B

Explanation:
Area of the wet surface =
2[lb+bh+hl] - lb = 2 [bh+hl] + lb
= 2[(4*1.25+6*1.25)]+6*4 = 49 m square

Q.3. A boat having a length 3 m and breadth 2 m is floating on a lake. The boat sinks by 1 cm when a man gets into it. The mass of the man is :
A. 50 kg
B. 60 kg
C. 70 kg
D. 80 kg

Answer: Option B

Explanation:

In this type of question, first we will calculate the volume of water displaces then will multiply with the density of water.
Volume of water displaced = 3*2*0.01 = 0.06 m cube

Mass of Man = Volume of water displaced * Density of water

= 0.06 * 1000 = 60 kg

Q.4. How many bricks, each measuring 25cm*11.25cm*6cm, will be needed to build a wall 8m*6m*22.5m
A. 6100
B. 6200
C. 6300
D. 6400

Answer: Option D

Explanation:

To solve this type of question, simply divide the volume of wall with the volume of brick to get the numbers of required bricks
So lets solve this

Number of bricks =
Volume of wallVolume of 1 brick=800*600*22.525*11.25*6=6400

Q.5. A swimming pool 9 m wide and 12 m long is 1 m deep on the shallow side and 4 m deep on the deeper side. Its volume is:
A. 260
B. 262
C. 270
D. 272

Answer: Option C

Explanation:

Volume will be length * breadth * height, but in this case two heights are given so we will take average,

Volume=(12*9*(1+42))m312*9*2.5m3=270m3