What's the diameter of a circle with a circumference of 48 millimeters

Since we are given circumference, we think the formula for the circumference, which is 2(pi)r or (pi)d where r and d is the radius and diameter respectively.  the smarter formula of the 2 is (pi)d because it's d we want to find.  setting up our equation:
circumference = (pi)d
48 = (pi)d
dividing both sides by pi gives:
d = 15.29 millimeters

let me know if you have any questions!

Idon’t understand this but 90