S Chand ICSE Mathematics Class 9 Solution Seventeenth Chapter Circle – Circumference and Area Exercise 17A
(1) Find the circumference of the circles whose diameters are:
(i) 49 cm
(ii) 14 cm
(iii) 9.8 cm
(iv) 7 cm
Solution:
(2) Find the circumference of the circles whose radii are:
(i) 7 cm
(ii) 28 cm
(iii) 3.5 cm
(iv) 98 m
Solution:
(3) Find the circumference of the circles, if
(i) radious = 4.5 cm
(ii) diameter = 15 cm
Solution:
(4) Find the length of the diameter of the circle whose circumference are –
(i) 22 cm
(ii) 8.8 cm
(iii) 44 cm
Solution:
(5) Find the length of the of the radii of the circles whose circumference are:
(i) 11 cm
(ii) 55 cm
(iii) 13.2 cm
(iv) 440 m
Solution: (i) 2πr = 11
or, 2 x 22/7 x r = 11
or, r = 7/4
(6) Find the radii of the circles if circumference is : (π = 3.14)
(i) 100 m
(ii) 6.4 dm
Solution:
(7) The diameter of venus planet is 12,278 km. Find its circumference.
Solution:
(8) (i) Find the perimeter of semi-circular plate of radious 3.85 cm.
Solution:
(ii) The circumference of a circle exceeds the diameter by 16.8 cm. Find the radious of the circle. (π = 22/7)
Solution:
(9) A wire is in the form of a circle of radious 42 cm. It is bent into a square. Determine the side of the square.
solution:
(10) In fig 17.05, the radious is 3.5 cm. find the perimeter of the quarter of the circle. Correct to one decimal place.
Solution:
(11) (i) The inner circumference of a circular track is 440 m. Track is 14 m wide. Find the diameter of the outer circle of the track.
Solution:
(11) (ii) Te inner edge of a circular running track is 440 m long. If the track is 10 m wide. Find the length of the outer edge of the track.
solution:
(12) A garden roller has a circumference of 3 metres. How many revolutions does it make in moving a distance of 21 metres?
solution: ∴ Perimeter of garden roller = 3 m
∴ To cover the distance of 21 m
it moves = 21/3 = 7 times.
(13) A bicycle wheel, diameter 70 cm, is making revolution in 10 sec. At what speed in km/h is the bicycle travelling?
solution:
(14) A small cart is being driven at 10 km/hr. If each wheel is 91 cm in diameter, find the number of revolutions made by each wheel per minute.
solution:
(15) How long will a boy take to go four times round a circular field whose radious is 35 m, walking at 5 km/hr.
solution: ∴ Perimeter of circular field = 2π x 35
= 2 x 22/7 x 35 m
= 10 x 22 m
= 220 m
(16) A wheel of a cart is making 4 revolutions per second, If the diameter of the wheel is 84 cm, find its speed.
solution:
(18) A circular field has a perimeter of 660 m. A plot in the shape of a square having in vertices on the circumferences is marked in the field. Calculate the area of the square plot (π = 22/7)
solution:
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