A circular disc of area 0.64π m2 rolls down a length of 1.408 km. The number of revolutions it makes is : (Taken π = 22/7).
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e 280
Explanation:
Area = πr2
πr2 = 0.64π m2
r = 0.8 m
Circumference of disc = 2 π r = 2 × (22/7) × 0.8 = 5.02
Length = 1.408 km = 1408 m
The number of revolutions = 1408/5.02 = 280