Atower casts a shadow 11 feet long the distance from the top of the tower to the end of the the shadow is 61 feet how many feet tall is the tower?

This is very easy!! I have attached a picture I have drawn if you are a visual learner... well, everything else like computations is here. 
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This is the PYTHAGOREAN THEOREM!!
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If you don't know, it says that the lengths of the legs squared added together all equal the hypotenuse squared in a right triangle!!
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And if you want to know why the "triangle" has a right angle... well,  are towers slanted? I mean, other than the Leaning Tower of Pizza. I mean Pisa.
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So... we plug it in!!
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Formula: a^2 + b^2 = c^2.
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Plug it in: 11^2+ 61^2 = c^2
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c^2 = 3842.
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So now what?
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SQUARE ROOT OF EVERYTHING!!
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c = √3842.
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So? c = approximately 61.984.
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Hope I helped!!