It is given that AS = SD = DA
Therefore, ΔASD is an equilateral triangle. OA (radius) = 20 m
Medians of equilateral triangle pass through the circum centre (O) of the equilateral triangle ASD. We also know that medians intersect each other in the ratio 2: 1. As AB is the median of equilateral triangle ASD, we can write
Therefore, the length of the string of each phone will be 20√3 m.