You can focus on the two sub-triangles ABC and ACD
We know that they are both right triangles, because we're given that AC and BD are perpendicular.
The sides AB and AD are the hypothenuses of these triangles, so we know their length through the pythagorean theorem:
But since we're given , the expressions for AD and AB are actually the same expression. This proves that AD=AB, and thus that the triangle is isosceles.
Given:
The formula for total cost is
where, p is the price of item and s is the sales tax rate (as a percent).
You pay $14.77 for an item priced at $14.
To find:
The the tax rate.
Solution:
You pay $14.77 for an item priced at $14. So,
Total cost (T) = $14.77
Price of item (p) = $14
Putting T=14.77 and p=14 in given formula, we get
Multiply both sides by 100.
Divide both sides by 14.
Therefore, the tax rate is 5.5%.