Two ladders are leaning against a building, forming two similar triangles as shown below. The top of the longer ladder is 28 feet up the building's side. The top of the shorter ladder is 20 feet up the building's side and its base is 15 feet from the bottom of the building. What is the length of the longer ladder?

The length of the longer ladder is 35 ft

Step-by-step explanation:

Please check the attachment for a diagrammatic representation of the problem

We want to calculate the length of the longer ladder ;

We make reference to the diagram

Since the two right triangles formed are similar. the ratios of their sides are equal;

Thus;

20/15 = 28/x + 15

20(x + 15) = 15(28)

20x + 300 = 420

20x = 420-300

20x = 120

x = 120/20

x = 6

So we want to calculate the hypotenuse of a right triangle with other sides 28ft and 21 ft

To do this, we use the Pythagoras’ theorem which states that square of the hypotenuse equals the sum of the squares of the two other sides

Let the hypotenuse be marked x

x^2 = 28^2 + 21^2

x^2 = 1,225

x = √1225

x = 35 ft

yx = 36

step-by-step explanation:

cos f = opposite side/ hypotenuse

cos f = yw / yx

we know cos f = 4/9 and yw =16

4/9 = 16/yx

multiply each side by yx

4/9 yx = 16/ yx * yx

4/9 yx = 16

multiply each side by 9/4

9/4 * 4/9 yx = 16 *9/4

yx = 36