Ex 11.1, 10
An umbrella has 8 ribs which are equally spaced (see figure). Assuming umbrella to be a flat circle of radius 45 cm, find the area between the two consecutive ribs of the umbrella.
Area of rib = 𝟏/𝟖× Area of umbrella
Radius = r = 45 cm
Area of umbrella = Area of circle
= 𝜋𝑟2
= 𝝅 (45)2
= 22/7× "45 "× 45
= 22/7× 2055
Now,
Area of rib = 1/8× area of umbrella
= 𝟏/𝟖×𝟐𝟐/𝟕× 2025
= (11 × 2025)/(4 × 7)
= 𝟐𝟐𝟐𝟕𝟓/𝟐𝟖 cm2
Hence, Area between two consecutive rib = 22275/28 cm2

Made by

Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.

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