The video above shows you how to calculate the area of a circle if you know either the radius or the diameter.
The above video shows a visual explanation of the area formula. In other words, it shows you WHY the area of a circle equals pi times radius squared.
Pi is the name for a very long number: 3.1415926535897932384626433832795028841971...
The symbol for pi is: π
A scientific calculator has a button 'π' to press if you need to use pi.
Formula for area of a circle:
This means pi x radius x radius. (It does NOT mean pi x radius x 2)
Study and practice