A 6-foot spruce tree is planted 15 feet from a lighted streetlight whose lamp is 18 feet above the ground. How many feet long is the shadow of that tree?

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Answer 1 · 2018-03-18T17:59:53

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Let the length of the shadow be #L# ft.

From the given figure using the properties of similar triangles (i.e. the ratio of corresponding sides are equal.) we can write

#L/(15+L)=6/18#

#=>3L=15+L#

#=>2L=15#

#=>L=15/2=7.5# ft