Answer: 29
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Explanation:
x = length of segment DC
The three triangles in that diagram are similar, which allows us to form this proportion below
BD/AD = AD/DC
Apply substitution and solve for x.
BD/AD = AD/DC
4/10 = 10/x
4x = 10*10 ... cross multiply
4x = 100
x = 100/4
x = 25
DC is 25 units long
Therefore,
BC = BD + DC = 4 + 25 = 29
