solve the easiest riddle in the world?

[LamiaRubaiyat]

1=5
2=10
3=15
4=20
5=??

 

[Pig]

5=1
5=25
5=5

 

[thomt]

If you are buying apples @ 5c, then 5 = 25.
But if 1 = 5 as above, then 5 = 1.
That is not the easiest riddle in the world; this one is:
1 + 1 = ?

 

[Girija]

5=25. because you multipled the number by 5 every time.

 

[Bonustokens]

5=1