A man borrowed $500$ dollar from his friend and decided to return this amount in four installments of $150$ dollar each at the end of $3$, $6$ and $9$th month. Find the rate of simple interest p.a if the first installment is given in the beginning.
Solution-
I have used Principal = 350 dollar as 150 dollar already paid and simple interest = 100 dollar
On solving using formula i get answer as 38% (app)
But actual answer given is 36.36%
I think something wrong in my solution. But dont know where. Please help me to solve.