5thnonagonalnumber

<-- Enter nonagonal number statement
  

Calculate nonagonal number 5

The formula for nonagonal number n is as follows
Nn  =  n(7n - 5)
  2

Given n = 5, we have:
N5  =  5(7(5) - 5)
  2

N5  =  5(35 - 5)
  2

N5  =  5(30)
  2

N5  =  150
  2

N5 = 75