We are told that a person is standing 20 feet from a streetlight. Notice that the person, the streetlight and the shadow form two triangles.
We want to find how many times taller the streetlight is than the person if the person is 6 feet tall and the length of their shadow is 10 feet. We can assume that the triangles are similar, which means that their corresponding sides are proportional.
h/6 = 20+10/10
Here, h represents the height of the streetlight. Let's solve this equation for h!
The height of the streetlight is 18 feet. Now that we know the height of the streetlight, we can calculate how many times taller it is than the person by finding the quotient of 18 and 6.
18/6 = 3
This means that the streetlight is 3 times taller than the person.
Extra
Similar Figures
We can use similar figures to solve a lot problems in life. They are very useful for finding the sizes of figures that are complex to measure by hand. Let's see a few examples!
Tree heights
Tower heights
Width of a river
Big angles
More information about similar figures can be found on the following page.
