On a sunny day, the tree in your backyard casts a shadow of 16 feet. At the same time, you cast a shadow of 4 feet. You are 5 feet 3 inches tall.

How tall is the tree?

17.3 ft
21 ft
21.2 ft
12.2 ft

1 answer

To find the height of the tree using the proportionality of the heights and shadow lengths, we can set up a ratio based on the information given.

  1. Convert your height from feet and inches to just feet.

    • You are 5 feet 3 inches tall.
    • There are 12 inches in a foot, so: \[ 3 \text{ inches} = \frac{3}{12} = 0.25 \text{ feet} \]
    • Therefore, your height in feet is: \[ 5 + 0.25 = 5.25 \text{ feet} \]
  2. According to the problem, your shadow is 4 feet long and the tree's shadow is 16 feet long. We can set up the following proportion: \[ \frac{\text{Height of you}}{\text{Shadow of you}} = \frac{\text{Height of the tree}}{\text{Shadow of the tree}} \] Plugging in the known values: \[ \frac{5.25}{4} = \frac{h}{16} \] Here, \(h\) represents the height of the tree.

  3. Cross-multiplying to solve for \(h\): \[ 5.25 \times 16 = 4 \times h \] Calculating \(5.25 \times 16\): \[ 5.25 \times 16 = 84 \] So we have: \[ 84 = 4h \] Dividing both sides by 4 gives: \[ h = \frac{84}{4} = 21 \text{ feet} \]

Thus, the height of the tree is 21 feet.

So the correct answer from your options is 21 ft.