 Hello and welcome to the session. Let us discuss the following question today. The first and the last terms of an AP are 17 and 350 respectively. If the common difference is 9, how many terms are there and what is their sum? Now let us write the solution. Given to us as first term A is equal to 17, last term L is equal to 350, common difference D is equal to 9 and we have to find N and S. Now we know An is equal to A plus N minus 1 D. Where An is given to us that is the last term which is 350. So substituting the values it implies 350 is equal to 17 plus N minus 1 multiplied by 9 which implies 350 is equal to 17 plus 9 N minus 9 which implies 350 minus 8 is equal to 9 N which implies N is equal to 342 by 9. Now this gets cancelled by 38 so it implies N is equal to 38. Now sum of N terms is given by S is equal to N by 2 multiplied by A plus N so which is equal to N is equal to 38 so 38 by 2 multiplied by A is given to us 17 plus L is given to us 350 which is equal to this gets cancelled by 19 so 19 into 367 which is equal to 6973 so S is equal to 6973 hence N is equal to 38 and sum is equal to 6973 I hope you understood the question bye and have a nice day.