 Hello students. Let's work out the following problem. It says an electric fan is available for Rs. 600 cash or for Rs. 250 cash down payment followed by 3 monthly installments of Rs. 125 each. Find the rate of interest charged under the installment plan. So let's now move on to the solution. We are given that the cash price or CP of fan is Rs. 600 and the cash down payment is Rs. 250. Therefore, balance due that is after paying Rs. 250 balance due will be Rs. 600 minus 250 that is Rs. 350. Now we are given that the number of installments is equal to 3 and the amount of each installment is Rs. 125. Therefore, amount paid under installment scheme or in 3 installments is equal to Rs. 3 into 125 since there are 3 installments and amount of each installment is Rs. 125. So this is equal to Rs. 375 and also therefore interest paid under installment scheme is equal to Rs. 375 minus 350 that is balance due so it is equal to Rs. 25. Now principle for first month is equal to Rs. 600 minus 250 that is 350 that is the balance due. Now principle for second month is equal to Rs. 350 that is principle for the first month minus 125 that is installment paid in the first month so this is equal to Rs. 225. Now the principle for third month is equal to Rs. 225 that is the principle for second month minus the installment paid in second month and this is equal to Rs. 100. Now the total principle for one month is equal to sum of all these principles which is equal to Rs. 675. Now the interest is given by principle into rate into time upon 100. Now the interest paid under installment scheme is Rs. 25 let's name this as 1 and this as 2. So interest is equal to Rs. 25 principle is Rs. 675 time is 1 by 12 since we have obtained the principle for one month time will be 1 by 12. And the rate of interest we have to find and we will assume this to be Rs. 1% so the interest is given by 25 is equal to Rs. 675 into Rs. 1 upon 12 upon 100. So from this we have 2500 is equal to 675 upon 12 into Rs. So this implies 2500 into 12 is equal to 675 Rs. So this implies Rs. is equal to 2500 into 12 upon 675. So this implies Rs. is equal to 44.4% hence the rate of interest is 44.4%. So this completes the question and the session why for now take care have a good day.