Question

find the circumference of a circle is 22 CM then find its diameter

Answer 1

Solve the equation for the diameterof the circle, d= C/π. 
Divide the circumferenceby pi to get the answer.
Most probably the answer would be something about 7.006

Answer 2

circumference of a circle =2pie.r= 22

2×22÷7.r=22
r = 7÷2
d=7