Question 1181581
Radius of cone = 7 cm

circumference of base of cone = 2*pi*7 = 44cm

This is the length of arc of the sector 
with angle 320 deg

l = Theta/360 * 2 *pi*r

44 = 8/9 * 2*pi*r

Radius of circle = 9*44/16 pi

r=7.87 cm