Simple, we are going to find the diameter of the circle then divide it by 2.
Since it is a circle, divide the circle into 2, it is the diameter of the circle, it will be like:
Ф
The diameter can be found by dividing the circular garden into 2, we can place a line or anything straight or just measure using a measurement instrument.
Ф
Now that we have the diameter, divide it by 2.
Example: the diameter is 10meters.
Divide 10 meters by 2, it will be 5 meters, so therefore, we should place the pipe of the fountain in 5 meters inside the circle, measure using a metro tape.
Diameter Ф / 2 = The center, and also the radius of the pipe.
In short, find the radius of the circle using the diameter, the radius is found using the formula : diameter / 2 = radius.
What will I do?
I will find the diameter of the circular garden, this is found by dividing the garden into two, and then the diameter again is divided into two to get the radius, and then the result is going to be the distance between the circular garden line inside of the center.
View using the picture below, it can explain it to you further more.