Advertisements
Advertisements
Question
The areas of two circles are in the ratio 4: 9. What is the ratio between their circumferences?
Solution
Let the radii of the two circles be r and R, the circumferences of the circles be c and C and the areas of the two circles be a and A.
Now,
`a/"A" = 4/9`
`=> (pi"r"^2)/(pi"R"^2) = (2/3)^2`
`=> "r"/"R" = 2/3`
Now, the ratio between their circumferences is given by
`"c"/"C" = (2pi"r")/(pi"R"^2)`
`= "r"/"R"`
`=2/3`
Hence, the ratio between their circumferences is 2 : 3.
APPEARS IN
RELATED QUESTIONS
How many times a wheel of radius 28 cm must rotate to go 352 m? (Take `pi = 22/7`)
A sheet of paper is in the form of rectangle ABCD in which AB = 40cm and AD = 28 cm. A semicircular portion with BC as diameter is cut off. Find the area of remaining paper.
The radius of a circular garden is 100 m. There is a road 10 m wide, running all around it. Find the area of the road and the cost of levelling it at Rs 20 per m2. [Use π = 3.14]
A 7 m road surrounds a circular garden whose area is 5544 m2. Find the area of the road and the cost of tarring it at the rate of Rs.150 per sq m.
If the perimeter of a semi-circular protractor is 36 cm. Find its diameter.
In the adjoining figure, the crescent is formed by two circles which touch at the point A. O is the centre of bigger circle. If CB = 9 cm and DE = 5 cm, find the area of the shaded portion.
Find the area and perimeter of the circles with following: Diameter = 77cm
The distance around a circle is its ______.
Find the total cost of wooden fencing around a circular garden of diameter 28 m, if 1 m of fencing costs ₹ 300.
A dinner plate is in the form of circle. A circular region encloses a beautiful design as shown in the given figure. The inner circumference is 352 mm and outer is 396 mm. Find the width of circular design.
