Allison is 5 feet tall. One afternoon her shadow measured 2.5 feet. At the same time, the shadow of her favorite tree was 14.5 feet.

 
What is the height of the tree?

1 answer

To find the height of the tree using similar triangles, we can set up a proportion based on the height and the shadow lengths of Allison and the tree.

Let:

  • \( h \) = height of the tree
  • Height of Allison = 5 feet
  • Shadow of Allison = 2.5 feet
  • Shadow of the tree = 14.5 feet

The proportion based on the similar triangles is:

\[ \frac{\text{Height of Allison}}{\text{Shadow of Allison}} = \frac{\text{Height of the tree}}{\text{Shadow of the tree}} \]

Plugging in the values, we get:

\[ \frac{5}{2.5} = \frac{h}{14.5} \]

Now, we can simplify the left side:

\[ \frac{5}{2.5} = 2 \]

So the equation becomes:

\[ 2 = \frac{h}{14.5} \]

To find \( h \), we multiply both sides by 14.5:

\[ h = 2 \times 14.5 \]

Calculating this gives:

\[ h = 29 \]

Thus, the height of the tree is 29 feet.