a diamond weighing 2.5 carats was cut into two pieces. The two pieces were put on a balance scale, one on each side. An additional weight of 0.9 carats on one side was required to maintain balance. Find the weight, in carats, of the larger piece

Let weight of smaller piece be x.

Larger = x + 0.9
ATQ, x + x + 0.9 = 2.5
2x = 1.6
x = 0.8
Larger = 0.9 + 0.8 = 1.7 carats