The sides of a triangle are 17, 25, 28. The greatest altitude is of length:

420/17 84/5 15 None of these

420/17

From geometry greatest altitude is perpendicular to shortest side. $Δ=\frac{1}{2}AL.BC⇒AL=\frac{2Δ}{17}$ where $Δ^2=s(s-a)(s-b)(s-c)=210^2$