10th Class
Mathematics
Areas Related to Circles
Question Bank
MCQs - Areas Related to Circles
question_answer
A pendulum swings through an angle \[60{}^\circ \] and describes an arc 8.8 cm in length. Then, the length of pendulum is \[\left[ use\,\pi =\frac{22}{7} \right]\]
A)8.40cm
B)16.8cm
C)4.20cm
D)8.90cm
Correct Answer:
A
Solution :
As per question, length of an arc of a sector of angle, \[\theta =60{}^\circ \] \[l=\frac{\theta }{360{}^\circ }\times 2\pi r\] \[\Rightarrow \,\,\,8.8=\frac{60}{360{}^\circ }\times 2\times \frac{22}{7}\times r\] \[\Rightarrow \,\,8.8=\frac{1}{3}\times \frac{22}{7}\times r\Rightarrow r=\frac{8.8\times 21}{22}\]\[\therefore \,\,\,\,\,r=8.40\,\,cm\]