Here's how to calculate the circumference of a 75 cm exercise ball:

1. Convert centimeters to inches:

* There are approximately 2.54 centimeters in 1 inch.

* 75 cm / 2.54 cm/inch = 29.53 inches

2. Calculate the circumference:

* Circumference = π * diameter

* Diameter = 2 * radius

* Since we know the diameter (29.53 inches), we can plug it into the circumference formula:

* Circumference = π * 29.53 inches ≈ 92.95 inches

Therefore, a fully inflated 75 cm exercise ball should have a circumference of approximately 92.95 inches.