A person claims to lend his money at the rate of 40% p.a. simple interest. However he takes interest in advance when he lends a sum for one year. At what interest rate does he lend the money actually?

66.66%

Let 100 be the Principal, then 40 will be interest for one year

Now, since interest was already included in the sum, so the actaul sum will be 60

rate = \(\frac{40}{60}\) x 100 = \(\frac{2 }{3}\)% = 66.66%