10.  An umbrella has 8 ribs which are equally spaced (see Fig. ). Assuming umbrella to be a flat circle of radius 45 cm, find the area between the two consecutive ribs of the umbrella.


Answers (1)
D Devendra Khairwa

It is given that the umbrella has 8 ribs so the angle of each sector is 45o.

Thus the area of the sector is given by:- 

                                              \\Area\ =\ \frac{\Theta}{360^{\circ}}\ \times \pi r^2\\\\Area=\ \frac{45^{\circ}}{360^{\circ}}\ \times \pi \times 45^2\\\\Area=\ \frac{22275}{28}\ cm^2                                                

Hence the area between two consecutive ribs is       \frac{22275}{28}\ cm^2.