Saved Bookmarks
| 1. |
Exersice 12.1 ka 3 no |
|
Answer» Thanks ? The radius of 1st\xa0circle, r1\xa0= 21/2 cm (as diameter D is given as 21 cm)So, area of gold region = π r12\xa0= π(10.5)2\xa0= 346.5 cm2Now, it is given that each of the other bands is 10.5 cm wide,So, the radius of 2nd\xa0circle, r2\xa0= 10.5cm+10.5cm = 21 cmThus,∴ Area of red region = Area of 2nd\xa0circle − Area of gold region = (πr22−346.5) cm2= (π(21)2\xa0− 346.5) cm2= 1386 − 346.5= 1039.5 cm2Similarly,The radius of 3rd\xa0circle, r3\xa0= 21 cm+10.5 cm = 31.5 cmThe radius of 4th\xa0circle, r4\xa0= 31.5 cm+10.5 cm = 42 cmThe Radius of 5th\xa0circle, r5\xa0= 42 cm+10.5 cm = 52.5 cmFor the area of nth\xa0region,A = Area of circle n – Area of circle (n-1)∴ Area of blue region (n=3) = Area of third circle – Area of second circle= π(31.5)2\xa0– 1386 cm2= 3118.5 – 1386 cm2= 1732.5 cm2∴ Area of black region (n=4) = Area of fourth circle – Area of third circle= π(42)2\xa0– 1386 cm2= 5544 – 3118.5 cm2= 2425.5 cm2∴ Area of white region (n=5) = Area of fifth circle – Area of fourth circle= π(52.5)2\xa0– 5544 cm2= 8662.5 – 5544 cm2= 3118.5 cm2 |
|