Gate2020 cs Q10

10The figure below shows an annular ring with outer and inner radii as b and a, respect. The annular space has been painted in the form of blue color circles touching the and inner periphery of annular space. If the maximum n number of circles can be painted, then the unpainted area available in annular space is _____.

A
B
C
D

Option : B
Explanation :

Radius of inner circle = a
Radius of outer circle = b
Radius of small circle = (b - a)/2
area of donut shaped figure = π(b² – a²)
Area of each small circle =
total area of all small circle= n
Area of remaining portion

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