Question

To find the distance around a circular disc, multiply the diameter of the disc by 3.14. What is the distance around the disc when : 
(a) The diameter is 18.7 cm? 
(b) The radius is 6.45 cm?

Answer 1

Dear student,

We know, Circumference of circular disc=2×π×r=π×(2×r)but we know  D=2×r  where, D is diameter of circular discso, Circumference of circular disc=π×Da) Distance around a circular disc=π×D=3.14×18.7=58.718cmb)  Circumference of circular disc=2×π×r=2×3.14×6.45=40.506 cm

Regards

Answer 2

a) d = 18.7 
     x = 18.7 x 3.14 
       = 58.718 
b) r = 6.45 = d = 2 x 6.45 = 12.9
    x = 2 x 6.45 x 3.14 
       = 20.253 x 2  = 40. 506