Find the 11th term from the last term (towards the first term) of the AP : 10,7,4,...,–62.
The correct option is C: −32
Here, first term, a=10, common difference, d=7–10=–3, last term, l=–62,
Where, l=a+(n–1)d
To find the 11th term from the last term, we will find the total number of terms in the AP.
So, –62=10+(n–1)(–3)
i.e., –72=(n–1)(–3)
i.e., n–1=24
or, n=25
So, there are 25 terms in the given AP.
These are a1,a2,a3,a4,a5,a6,a7,a8,a9,a10,a11,a12,a13,a14,a15,a16,a17,a18,a19,a20,a21,a22,a23,a24,a25
The 11th term from the last term will be the 15th term from the start.
So, a15=a+(n−1)d
=10+(15–1)(–3)=10–42=–32
i.e., the 11th term from the last term is –32.