This set of Mathematics Multiple Choice Questions & Answers (MCQs) focuses on “Surface Areas and Volumes”.

1. Total surface area of a cuboid having dimensions l*b*h is __________

a) l*b*h

b) 2(lb + bh + lh)

c) lb + bh + lh

d) 6l^{2}

View Answer

Explanation: As shown in the figure below,

The total surface area of a cuboid is the sum of the area of six rectangles constituting the cuboid.

The six rectangles forms three pairs of rectangles (which are at opposite sides) who have the same surface area.

Area of one pair of rectangles having sides l and b = 2(l*b)

Area of the second pair of rectangle having sides b and h = 2(b*h)

Area of the third pair of rectangle having sides l and h = 2(l*h)

The total area of the cuboid = sum of three pairs of rectangles

= 2(l*b) + 2(b*h) + 2(l*h)

= 2(lb + bh + lh).

2. Total surface area of a cube having sides l is given by __________

a) l*b*h

b) 2(lb + bh + lh)

c) lb + bh + lh

d) 6l^{2}

View Answer

Explanation: A cube has six equal sides.

Hence, total surface area of a cube = sum of areas of 6 sides (as shown in the figure below)

Area of one side of a cube having side equal to ‘l’ = l

^{2}

Total surface area of the cube = l

^{2}+ l

^{2}+ l

^{2}+l

^{2}+ l

^{2}+ l

^{2}

= 6l

^{2}.

3. A cube of side equal to 20 cm is open from the top. Its total surface area is __________ cm^{2}.

a) 2000

b) 2400

c) 2500

d) 8000

View Answer

Explanation: The cube is open from the top, hence total surface area of the cube will be equal to 6l

^{2}– l

^{2}= 5l

^{2}

= 5(20)

^{2}

= 5(400)

= 2000.

**Sanfoundry Global Education & Learning Series – Mathematics – Class 9**.

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