Is there a difference between んがため and ために?

Question

My JLPT textbook has a section about the use of んがため, which they define as "making an effort in order to realize the intended purpose." Which to me sounds like plain ol' ために. For example, they have this example sentence: > 祖父{そふ}は１００歳{さい}まで生{い}きんがために、食生活{しょくせいかつ}にはとても気{き}をつける。 Isn't that the same as saying: > 祖父{そふ}は１００歳{さい}まで生{い}きるために、食生活{しょくせいかつ}にはとても気{き}をつける。 ...?

Answer 1

To me, both sounds correct. んがためにmeans old time of expression. 　ために is modern word we use.

Like I said, both are correct and no any difference.