Quote 'If this is how they worked out area how did they do circumferences?'
One way they did it with the Egyptian value for pi 3.1604.
Take the length of the Great pyramid 440 RC and make it the diameter of a circle (a circle inscribed into the base of the GP)
1. 440 / 9 = 48.888888 and you do that by construction then measure to the 8th space = 391.1111 This the side of a square the area of which equals the area if a circle.
2. To find the circumference of the circle using 3.1604 repeat the process.
391.1111 / 9 = 43.45679012 measure to the 8th space or multiply by 8 = 347.654321 (notice the progressions here with these 2 numbers.
347.654321 is the side of a square the perimeter of which equals the circumference of the circle with diameter 440 and using 3.160493827