Answer:
The diameter of the white blood cell in millimeters is 3 mm.
Explanation:
Given : The diameter of a white blood cell under magnification appears to be 0.3 centimeters.
To find : What is the diameter of the white blood cell in millimeters?
Solution :
The diameter of a white blood cell is 0.3 centimeter.
Conversion of centimeter into millimeters,

So, 0.3 cm into mm is



Therefore, the diameter of the white blood cell in millimeters is 3 mm.