Mark B. answered 02/10/19
PhD Candidate in Psychology: Experienced Math, Statistics, Tutor
Hello Laia,
As I suspect you are aware this is a Pythagorean theorem problem. I always recommend to my students in classes to draw the information given to make it easier to solve.
Since I cannot draw this for you, let me explain the way the right angle is situated. The right angle is located at the bottom of the building where it reaches the building.
We know the top of the ladder reaches a height of 28 feet and we know the hypotenuse of this right angle is unknown. Therefore, the missing value is the distance from the building to the ladder at the base and this creates the following equation:
a2 + b2 = c2
We already know the leg of this right triangle is unknown. But we do know the hypotenuse is 30, and the height - which provides the final leg is 28 feet. Now, let's substitute the values.
a2 + b2 = c2
a2 + 282 = 302
a2 + 784 = 900
a2 = 116
a = √116
a ≈ 10.77
When rounded, you can see that the answer now becomes 10.8 feet.
I hope I have helped and you have a great week. Best.