The true daily interest rate, assuming 365 days, is 1.121/365 − 1 ≈ 0.031054%. To compute your true rate of return, compound this over 7 days: (1 + 0.03105%)7 = 1.000310547 ≈ 1.0021758. (You could also compute the rate of return differently: There are 52.15 weeks in 365 days. Therefore, r = (1 + 12%)(1/52.15) − 1 ≈

1.0021758.) Your $100,000 will grow into $100,217.58. You would have earned $217.58 in interest.