Question

An umbrella has 8 ribs which are equally spaced (as shown in the figure). Assuming the umbrella to be a flat circle of radius 42 cm, find the area between the two consecutive ribs of the umbrella.

Answer 1

Ribs are equally spaced

$\Rightarrow$ There angle and the centre of circle

will also be equal and their area

will also be equal.

Total area of circle $=\pi r^2$

$\Rightarrow$ Area between two consecutive ribs $=\frac{\pi r^2}{8}$

$r=42c.m.$

$\Rightarrow Area=\frac{22}{7}\times \frac{42\times 42}{8}=11\times 21\times 3$

$=693c.m^2$