Correct Answer - Option 3 : 1320 m
2
Given:
The distance is travelled by him = 10 km
Reaching time = 50 minutes
⇒ (5/6) hours
The volume of a cylinder = 4620 m3
And the height of a cylinder = 30 m
The volume of a cone = (1/7) × the volume of a cylinder
And the height of a cone = 10 m
Reduce time = (50 - 10)
⇒ 40 minutes
⇒ 40/60 hours
⇒ 2/3 hours
Formula used:
Speed = (Distance/Time)
The volume of cylinder = πr2h
The curved surface area of a cylinder = 2πrh, where r is the radius of a cylinder and h is the height of a cylinder.
The volume of a cone = (1/3)πR2H, where R is the radius of a cone, H is the height of a cone and π is 22/7
The slant height of a cone = √(height2 + radius2)
Calculation:
The volume of cylinder = (22/7) × r2 × 30
⇒ 4620 = (22/7) × r2 × 30
⇒ r2 = (4620 × 7)/(30 × 22)
⇒ r2 = 49
⇒ r = √(49)
⇒ r = 7 m
The curved surface area of a cylinder = 2 × (22/7) × 7 × 30
⇒ 1320 m2
∴ The curved surface area of a cylinde is 1320 m2