1. RAYAT SHIKSHAN SANSTHA’S
SHRIMAN SHETH GANPATRAO SURYAWANSHI VIDYALAYA TAMBAVE TAL. PHALTAN DIST SATARA

2. THE CIRCUMFERENCE AND AREA OF A CIRCLE
SUB- MATHEMATICS
STD- 8th
TOPIC
THE CIRCUMFERENCE AND AREA OF A CIRCLE

5. CIRCUMFERENCE OF A CIRCLE
C=2πr
C= CIRCUMFERENCE OF A CIRCLE
π=22/7 0R 3.14
r = RADIUS OF A CIRCLE

6. THE RELATION BETWEEN DIAMETER AND RADIUS OF A CIRCLE
d=2r d= Diameter of a circle r= Radis of a circle

7. The ratio circumference to diameter of any circle remains constant and that is 22/7 or 3.14
c/d=π
=22/7 or 3.14

8. PROBLEMS BASED ON CIRCUMFERENCE OF A CIRCLE
Q. THE RADIUS OF A CIRCLE IS 14cm. FIND THE CIRCUMFERENCE OF THE CIRCLE ?
SOLUTION-
GIVEN-
r= 14cm
π= 22/7
c = ?
FORMULA
C=2πr
=2*22/7*14
=2*22*2
=88 cm
HENCE CIRCUMFERENCE OF A CIRCLE= 88cm

9. Q. IF THE CIRCUMFERENCE OF A CIRCLE IS 176m
Q.IF THE CIRCUMFERENCE OF A CIRCLE IS 176m. THEN FIND THE RADIUS OF THE CIRCLE.
SOLUTION-
GIVEN-
C= 176m
π= 22/7
r= ?
FORMULA
C=2πr
176 =2*22/7*r
176*7 =44*r
1232/44 =r
28 =r
HENCE RADIUS OF A CIRCLE=28m

10. AREA OF A CIRCLE A=πr2 A=AREA OF A CIRCLE π= 22/7 or 3.14
r= RADIUS OF A CIRCLE

11. IF RADIUS OF A CIRCLE IS 7CM. THEN FIND THE AREA OF THAT CIRCLE.
SOLUTION
R= 7cm
Π= 22/7
FORMULA
A=πr2
= 22/7*(7)2
= 22/7*49
= 22*7
= 154 sqcm.
HENCE THE AREA OF THE CIRCLE IS 154sq.cm

12. IF THE AREA OF A CIRCLE IS 154sq.cm THEN FIND THE RADIUS OF THE CIRCLE .
SOLUTION
A= 154sq.cm
Π = 22/7
R = ?
FORMULA
A=πr2
=22/7*(r)2
154*7 =22*(r)2
1078 = 22*(r)2
1078/22=(r)2
49=(r)2
7=r
HENCE THE RADIUS OF THE CIRCLE IS 7 cm.

13. IF CIRCCUMFERENCE OF A CIRCLE IS 88cm THEN FIND THE AREA OF A CIRCLE.
C= 88cm
A= ?
FORMULA
C = 2πr
88 = 2*22/7*r
88*7 = 44*r
616/44 = r
r= 14cm
A=πr2
= 22/7*(14)2
= 22/7*196
= 22*28
= 616 sqcm.
HENCE THE AREA OF THE CIRCLE IS 616 sq.cm

14. END