Three circles of radius 7 cm are kept touching each other. The string is tightly tied around these three circles. What is the length of the string?

Correct option is C

Given:

Three circles of radius 7 cm are kept touching each other.

The string is tightly tied around these three circles

Formula used:

Circumference of circle = 2πr

​Solution:​

According to the question, 

The length of the string not in contact with the circle,

=> 2r + 2r + 2r = 6r

=> 6 × 7 = 42

By symmetry, the angles swiped by a string on one circle is 120.

Length of string touching circle,

​$$=> (\frac{2πг}{3}) + (\frac{2πг}{3}) + (\frac{2πr}{3}) = 2πr=> 2 × 7 × π = 14π$$​​

Total length = 42 + 14π.

∴ The length of the string is 42 + 14π.