Learning about math, the hands on way, is often a lot more understandable by the children. It is also a lot more fun.
In the video we made a large round flower bed without using a calculator. 22/7 is almost the same as PI.
To understand the relationship between the circles diameter and circumference, we first put 7 tiles as the diameter, then 22 tiles around them in a circle.
The relationship between a circles diameter and circumference is 𝛑, which is very close to 22/7, or around 3.14 in decimals. The fraction 22/7 is not exactly 𝛑, but 0.4‰ greater, but when you are making a flower bed it will still work out, even with this imprecision.