In this page we have *Practice questions for Mensurations Class 8 maths Chapter 9* . Hope you like them and do not forget to like , social share
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There are two cuboidal whose dimensions are given below. Which box requires the higher amount of material to make?

Cuboid A: L=23, B=30, H=40

Cuboid B: L=30, B=12, H=44

Material will be measures by the surface area

Surface Area of Cuboid A= 2(LB + BH+ LH) = 2(23 *30 + 30*40 + 23 *40) =2*2810 cm^{2}

Surface Area of Cuboid B= 2(LB + BH+ LH) = 2(30*12 + 12*44 + 30 *44) =2*2208 cm^{2}

So Cuboid A will require the higher amount of material to make

Three cubes, each of edge 2 cm. long are placed together. Find the total surface area of the cuboid so formed?

L = 2+ 2 + 2= 6 cm

B=2 cm

H=2 cm

Surface Area of Cuboid = 2(LB + BH+ LH) = 2(6 *2 + 2*2 + 6 *2) =56 cm^{2}

Find the side of a cube whose surface area is 2400 cm

Surface of cube= 6a^{2}

So , 6a^{2}=2400

a=20 cm

Meghna painted the outside of the cabinet of measure 2 m × 3 m × 2.5 m. How much surface area did she cover if she painted all except the bottom of the cabinet and back side?

Here L=2 m, B=3 m and H=2.5 m

Total surface area of a cuboid =2LB+2BH+2LH
Now is she left bottom and back side of box area covered is
=2LB+2BH+2LH-LB-LH
= LB+2BH+LH
=(2*3)+2(3*2.5)+(2.5*2)
= 26m^{2}

Ahmed is painting the walls and ceiling of a cuboidal hall with length, breadth and height of 25 m, 12 m and 8 m respectively. From each can of paint 200 m² of area is painted. How many cans of paint will she need to paint the room?

Here L=25 m, B=12 m and H=8 m

Area to be painted= Area of lateral surface + Area of Ceiling

=2(LH) + 2(BH) + LB

=892 m^{2}

Theerefore, no of cans required= 892/200

=4.5 cans

A open cylindrical tank of radius 14 m and height 3 m is made from a sheet of metal. How much sheet of metal is required?

here r=14 m and h=3 m

Sheet of metal require = total surface area of Cylinder = 2 π rh + π r^{2}

=880 m^{2}

The lateral surface area of a hollow cylinder is 4224 cm

Here B= 33 cm

Area of Rectangular Sheet formed = Surface Area of the Cylinder

Area of Rectangle = L × B

Therefore

L × B= 4224

Putting the value of B and solving

L=4224/33=128 cm

Now

Perimeter Of Rectangle=2(L+B) = 2(128+33)

=322cm

A road roller takes 750 complete revolutions to move once over to level a road. Find the area of the road if the diameter of a road roller is 154 cm and length is 1 m.

Length of roller = 1m = 100cm , Diameter of road roller = 154 cm

Circumference of roller = 2 π r= π D = 22/7 * 154 = 484 cm

Now Length travelled in 1 rev= Circumference of road roller

Therefore

Length of road = Length travelled in 750 = 750 * Circumference of road roller = 363,000 cm

Width of road = length of roller = 100 cm

Area of road = Area of rectangle = L * B = 363,000 * 100 = 363 * 10^{5} cm ^{2}

A rectangular sheet of metal foil is 88 cm. long and 20 cm. wide. A cylinder is made out of it, by rolling the foil along width. Find the volume of the cylinder.

L = 88 cm

B= 20 cm

As per the question,Since cylinder is made out of it, by rolling the foil along width ,the circumference will be equal to the breadth of the sheet and the length will be the height of the cylinder.

Circumference=2 π r= 20 cm

or r= 10/π

Height of the cylinder = 88 cm

Now volume = π r^2 h = 88 *100/π = 2800 cm^{2}

The perimeter of the floor of a hall is 250 m. If the height is 4 m, find the cost of painting the four walls at the rate of Rs. 12 per square meter.

Surface area to be painted = 2(LH+BH) = 2H(L+B)

given perimeter of floor = 250m = 2(L+B)

and height is 4m

Substituting these values

Surface area=1000 m^{2}

cost of painting 1 square metre=Rs 12

cost of painting 1000 square metre=1000*12= Rs 12000

How many times do the volume and surface area of a cube increase if its edges get tripled.

$V_1=L^3$ and $SA_1= 6L^2$

$V_2= (3L)^3 = 27L^3$ and $SA_2=6(3L)^2 = 9 \times 6L^2$

So, Volume becomes 27 times and Surface Area become 9 times

How many times do the volume and Lateral surface area of a cylinder increase if its radius doubled and height remains same

$V= \pi r^2 h$ and $SA= 2 \pi rh$

If radius is doubled and height remains same ,then

$V_2= \pi (2r)^2 h = 4 \pi r^2 h$

$SA_2 = 2 \pi (2r) h =2 \times 2 \pi rh$

So volume becomes four times and Surface area becomes doubled

How many times do the volume and Lateral surface area of a cylinder increase if its radius remains same and height is doubled

$V= \pi r^2 h$ and $SA= 2 \pi rh$

if its radius remains same and height is doubled ,then

$V_2= \pi r^2 (2h) = 2 \pi r^2 h$

$SA_2 = 2 \pi r (2h) =2 \times 2 \pi rh$

So volume becomes doubled and Surface area becomes doubled

The height of a cylinder is 30 cm. and curved surface area is 660 cm

$2 \pi rh= 660$

$ 2\times (22/7) \times r \times 30 = 660$

r=3.5 cm

This Practice questions for Mensurations Class 8 maths is prepared keeping in mind the latest syllabus of CBSE . This has been designed in a way to improve the academic performance of the students. If you find mistakes , please do provide the feedback on the mail.

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