Answer:
Since the decoration is in the shape of a triangle, we can use the formula for the area of a triangle to solve for its height. The area of a triangle is given by:
Area = (1/2) x base x height
Let's call the height of the decoration h. We know that the base after firing is 9 inches, so we can plug in the given values and solve for h:
Area = (1/2) x 9 x h
Area = 4.5h
We don't know the exact area of the decoration, but we do know that the decoration maintains its shape after firing. This means that the ratio of the areas before and after firing is the same, and so is the ratio of the heights and bases. Since the height and base are proportional, we can write:
h / 15 = 9 / 10
Simplifying the equation, we get:
h = (9/10) x 15
h = 13.5
Therefore, the height of the finished decoration is 13.5 inches.