Question

please give me this question answer​

Answer 1

Step-by-step explanation:

Let the radius of the circle be r cm and the arc Ab of length 5π cm subtends abgle θ at the centre O of the circle. Then , 

Arc AB=5 π cm and Area of sector OAB=20 πcm2

⇒360θ×2πr=5πand360θ×πr2=20π

⇒360θ×2πr360θ×πr2=5π20π

⇒2r=4

⇒    r=8cm 

We have  Area = 21lr

⇒20π=21×5π×r

⇒r=8cm