As a Youngster, You Drive a Nail in the Trunk

As a youngster, you drive a nail in the trunk of a young tree that is 3 meters tall. The nail is about 1.5 meters from the ground. Fifteen years later, you return and discover that the tree has grown to a height of 30 meters. About how many meters above the ground is the nail?

A) 0.5
B) 1.5
C) 3.0
D) 15.0