 Hello and welcome to the session. In this session we discuss the following question which says at what rate per annum will rupees 4000 amount to rupees 6000 in 2 1 upon 2 years. We know that amount is equal to principal plus simple interest and the simple interest that is s i is equal to p into r into t upon 100 where this p is the principal r is the rate of interest per annum t is the time in years. This is the key idea to be used in this question. Let's proceed with the solution now. In the question we are given that the principal p is given as rupees 4000 and the amount a is given as rupees 6000 then the time t is two and a half years or you can say 5 upon 2 years. Now we need to find the rate of interest per annum that is r. Now since we know that amount is equal to principal plus simple interest that is amount a is equal to principal plus the simple interest s i so this means the simple interest s i is equal to amount minus principal that is s i is equal to rupees 6000 minus rupees 4000 which means simple interest is equal to rupees 2000. Now we know that the formula for simple interest s i is equal to principal p into rate of interest per annum r into time t upon 100. Now substituting the values for p, t and s i we get 2000 is equal to 4000 into r into 5 upon 2 and this whole upon 100. So from here we get r is equal to 2000 into 100 upon 4000 into 5 upon 2 this means that r is equal to 2000 into 100 into 2 upon 4000 into 5. Now solving this we get 2, 2 times is 4 this 2 cancels with this 2 and 5 20 times is 100 so this is equal to 20 thus we get r is equal to 20 percent per annum. So the rate of interest r is equal to 20 percent per annum. So 20 percent per annum is the final answer. This completes the session. Hope you have understood the solution for this question.