Question

4. The lateral surface area of a
right circular cone of height 28
cm and base radius 21 cm(in sq.
cm) is:​

Answer 1

Answer:

h=28 cm

r=21cm

l2=r2+h2

l2=441+784

l2=1225

l=35cm

lateral surface area =

pi×r×l

22/7×21×35

22×21×5

2310cm2

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Answer 2

Given :-

• Height of circular cone (h) = 28cm
• Radius of cone (r) = 21cm

To find :-

• Lateral surface area of cone

Solution :-

As we know that

→ l = √r² + h²

→ l = √(21)² + (28)²

→ l = √441 + 784

→ l = √1225 = 35cm

Therefore, slant height (l) of a cone is 35cm

Now, lateral surface area of cylinder

→ πrl

→ 22/7 × 21 × 35

→ 22 × 3 × 35

→ 2310cm²

Hence,

• Lateral surface area of cone is 2310cm²

Extra Information :-

• Volume of cylinder = πr²h
• T.S.A of cylinder = 2πrh + 2πr²
• Volume of cone = ⅓ πr²h
• C.S.A of cone = πrl
• T.S.A of cone = πrl + πr²
• Volume of cuboid = l × b × h
• C.S.A of cuboid = 2(l + b)h
• T.S.A of cuboid = 2(lb + bh + lh)
• C.S.A of cube = 4a²
• T.S.A of cube = 6a²
• Volume of cube = a³
• Volume of sphere = 4/3πr³
• Surface area of sphere = 4πr²
• Volume of hemisphere = ⅔ πr³
• C.S.A of hemisphere = 2πr²
• T.S.A of hemisphere = 3πr²