In △ABC, AD, BE and CF are medians, and G is centroid. If AD=15 cm, find AG.
We know that centroid divides a median in the ratio 2:1.
So, G divides AD in the ratio 2:1.
Let GD=x, then AG=2x.
∵AD=AG+GD
∴15=2x+x
⇒3x=15
⇒x=153=5 cm
⇒AG=2x=2×5=10 cm