Question

.The area of the ring between two concentric circles is 3168 cm². Find the radii of the t
circles if (i) their sum is 42 cm and (ii) their difference is 28 cm.


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Answer 1

Answer:

7 cm & 35 cm

Step-by-step explanation:

Let the radius of the outer circle be $r_{1}$ and of the inner circle be $r_{2}$

Then,

$r_{1}$ + $r_{2}$ = 42          . . . . . (1)

and

$r_{1}$ - $r_{2}$ = 28

⇒ $r_{1}$ = $r_{2}$ + 28          . . . . . (2)

Replacing value of $r_{1}$ in equation (1)

$r_{2}$ + 28 + $r_{2}$ = 42

⇒ 2$r_{2}$ = 42 - 28 = 14

⇒ $r_{2}$ = 7

and

$r_{1}$ = $r_{2}$ + 28 = 7 + 28 = 35