A man stands 9 metres from the base of a tree. He knows the distance from where he is standing and the top of the tree is 15 metres. How tall is the tree?

a2 + b2 = c2

a : 9       b : unknown      c: 15

b2 =c2 - a2

so b2 = 225 - 81

=144 so b=12

JM

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