Capital budgeting

A bank offers different bank accounts with different interest rates Bank account 1 = 10% interest per year, interest calculated quarterly Bank account 2 = 12% interest per year, interest calculated monthly Bank account 3 = 1.2% interest per month Bank account 4 = 3% interest per quarter Solution: 1. (1+0.1/4) ^4-1 X 100 = 10.38% 2. (1+0.12/12) ^12-1 X 100 = 12.68% 3. (1+0.012) ^12-1 X 100 = 15.39% 4. (1+0.03) ^4 -1 X 100 = 12.55% I don’t get it we have formula where R = (1 + i/n) ^ n -1 The first two solutions have been divided by "n", but in the case of the last two (3 and 4) they did not divide by “n” (In the 3rd case it's 12 and in the 4th case is 4). can you explain why? thanks in advance