If 21st term of an A.P is 25 find the sum of its first 41 term
Answer»
Let the A.P be a,a+d,a+2d......... given that a+20d =25 so a=25-20d. sum of 41 terms will be 41\2*[2a+(41-1)d] put VALUE of a here we GET 41\2[50-40d+40d] sum=41*25=1025 hope this answer will HELP u please follow me if u like my answer.