How many triangles are there in the given figure:

25 27 28 29

27

Here When n is even: No. of triangles = \(\frac{n\;(n\;+\;2)(2n\;+\;1)}{8}\)                        = \(\frac{4\;(4\;+\;2)(8\;+\;1)}{8}\)                        = \(\frac{216}{8}\) = 27