 Hi and welcome to the session, let's work out the following question. The question says the cash price of a machine is Rs 9000. It is also available at Rs 2200 cash down payment followed by 5 equal monthly installments of Rs 1400 each. Find the rate of interest under the installment plan. So let's start with the solution to this question. It's given to us in the question that price of machine is equal to Rs 9000 on cash down payment of Rs 2200 is also available. Therefore the balance amount is Rs 9000 minus 2200 that is equal to Rs 6800. Now number of installments that is n is equal to 5. Value of each installment that is the principle is Rs 1400. We have to find the rate of interest. Now we know that at the end of installment plan total value of balance amount is equal to future value of all installments or we can put it mathematically as 1 plus nr divided by 1200 multiplied by the balance amount is equal to 1 plus n minus 1 into r divided by 2400 multiplied by n into p. Now we know that n is equal to 5 and p is Rs 1400. So this implies 1 plus 5r divided by 1200 multiplied by 6800 is equal to 1 plus 5 minus 1 into r divided by 2400 multiplied by 5 into 1400 this implies 1200 plus 5r divided by 1200 multiplied by 6800 is equal to 2400 or we can write this as 1 plus 4r divided by 2400 into 7000 this implies 1200 plus 5r into 6800 divided by 1200 is equal to 1 plus 2r divided by 1200 into 7000 Now this implies that 1200 plus 5r into 6800 is equal to 1200 plus 2r into 7000 this implies 1200 plus 5r into 68 is equal to 1200 plus 2r into 70 this implies 1,600 plus 340 r is equal to 84,000 plus 140 r this implies 340 r minus 140 r is equal to 84,000 minus 81,600 this implies 200 r is equal to 2400 dividing both the sides by 200 we get r is equal to 2400 divided by 200 that further simplifies to 12. So our answer to this question is that rate of interest under this installment plan is 12%. So I hope that you understood the solution and enjoyed the session. Have a good day.