One of the most important question from arithmetic progression chapter as it was already asked in previous year paper of 2015 in which we have to determine the last term and the sum of its last 10 terms if An AP 8, 10, 12,……has 60 terms.
RS Aggarwal, Class 10, chapter 5C, question no 34(ii).
A.P is 8,10,12………………….
Then first term is 8 and common difference is 2.
an=a+(n−1)d.
Then a60=8+(60−1)2=8+59×2=126
Last 10 term =a51,a52..................a60
Then a51=8+(51−1)2=108
So total of last 10 terms=10/2[108×2+(10−1)2]
=216+81
=234×5
=1170