Advertisements
Advertisements
Question
The area of a circle is 38.5 cm2. The circumference of the circle is
Options
6.2 cm
12.1 cm
11 cm
22 cm
Solution
22 cm
Let the radius be r cm.
We know:
Area of a circle
= πr2 cm2
Thus, we have
πr2 = 38.5
`=>22/7xx"r"^2 = 38.5`
`⇒ r^2 = (38.5xx7/22)`
`=> "r"^2 = (385/10xx7/22)`
`=> "r"^2 = 49/4`
`=> r = 7/2`
Now,
Circumference of the circle = 2πr
`= 2 × 22/7xx"r"`
`=(2xx22/7xx7/2)`
= 22 cm
APPEARS IN
RELATED QUESTIONS
The circumference of a circle is 39.6 cm. Find its area.
A wire when bent in the form of an equilateral triangle encloses an area of `121sqrt(3) "cm"^2`. The same wire is bent to form a circle. Find the area enclosed by the circle.
The length of a chain used as the boundary of a semicircular park is 108 m. Find the area of the park.
The wheels of a car make 2500 revolutions in covering a distance of 4.95 km. Find the diameter of a wheel.
A wire when bent in the form of a square encloses an area of 484 cm2. If the same wire is bent into the form of a circle, find the area of the circle.
Find the area grazed by a horse tied with a 11. 2 m rope to a corner of a field measuring 25m by 15 m.
The diameters of the front and the rear wheels of a tractor are 63 cm and 1.54 m respectively. The rear wheel is rotating at `24 6/11` revolutions per minute. Find:
(i) the revolutions per minute made by the front wheel.
(ii) the distance traveled bu the tractor in 40 minutes.
Find the number of revolutions made by a circular wheel of area 1.54 m2 in rolling a distance of 176 m.
Find the total cost of wooden fencing around a circular garden of diameter 28 m, if 1 m of fencing costs ₹ 300.
The circumferences of two circles are in the ratio 4 : 5. What is the ratio of their radii?
