NECO 2023 · Paper 1 · Q12

In an arithmetic progression, the first term is 3 and the sum of the 3rd and 12th terms is $38\frac12$ . What is the 17th term?

Worked solution (try it first)

With $a = 3$ , the 3rd term is $3 + 2d$ and the 12th term is $3 + 11d$ .
Their sum gives $6 + 13d = 38\frac12$ , so $13d = 32\frac12$ and $d = 2\frac12$ .
The 17th term is $a + 16d$ , which is $3 + 16 \times 2\frac12 = 43$ , option B.