Question

Find the lateral surface area of two pillars if height of the pillar is 7m and radius of the base is 1.4m.



a) 112.3cm²
b) 123.2m²
c) 90m²
d) 345.2cm²​

Answer 1

To Find:-

• The lateral surface area of two pillars

solution:-

step-by-step explanation:

Given, height of the pillar = 7m and

Radius of the base = 1.4m

So, We know that

Lateral surface area of two pillars

= 2 × Curved surface area

According the question,

∴ 2 × 2πrh

$= 2 \times 2 \times \dfrac{22}{7} \times 1.4 \times 7$

$= 2 \times 2 \times 22 \times 1.4$

$= 4 \times 22 \times 1.4$

$= 88 \times 1.4$

$\bf{ = 123.2 {m}^{2}}$

Required Answer:

Option b ( 123.2m² ) is the correct answer.

$\bf{ \star \: Key \: Concepts \:\star}$

• Volume of Cylinder = πr²h cubic units
• Total surface area of cylinder = 2πr( h + r ) sq.units
• Curved surface area of cylinder = 2πrh sq.units
• Diagonal of a cube = a√3 units
• Lateral surface area of a cube for = 4a² sq.unit
• Volume of a cube = a³ cubic units.
• Diagonal of a cuboid = $\sqrt{L² + b² + h²}$
• Volume of a cuboid = ( L + b + h ) cubic units.

Answer 2

Given

• Radius of the pillar (r) = 7m
• Base of the pillar (b) = 1.4m

To find

• Lateral surface area of two pillars.

Solution

$\underline{\boxed{Curved\: surface\: area\: of\: cylinder = 2πrh}}$

→ C.S.A of one pillar = 2 × 22/7 × 7 × 1.4

→ C.S.A of one pillar = 44 × 14/10

→ C.S.A of one pillar = 61.6 m²

Now,

→ C.S.A of two pillars = 2 × 61.6

→ C.S.A of two pillars = 123.2 m²

$\rule{200}3$

Hence, option (b) is correct.