Suppose an investment offers to quintuple your money in 30 months (dont believe it). What rate of return per quarter are you being offered?

I came up with 2 ways to calculate it but got different answer. The first one is correct, but I can't figure out what's wrong with the second method.

First one: N=10, PV=-1, FV=5, PMT=0, I=17.46%

Second one: N=30, PV=-1, FV=5, PMT=0, I=5.51%*3=16.53%