Question

A pendulum swings through an angle of 30 and describes an arc 8.8cm in length. find the length of the pendulum

Answer 1

11/21 * r = 8.8
r = 16.8 = length of the pendulum

Answer 2

length of arc = 8.8 cm
$2\pi \times r \times 30 \div 360 = 8.8 \\ = 2 \times 22 \div 7 \times r \times1 \div 12 = 8.8 \\ r = 8.8 \times 7 \times 12 \div 2 \times 22 \\ r = 739.2 \div 44 \\ r = 16.8cm$
so req. length of pendulum is 16.8 cm