JAMB 2001 · UME · Q14

The sixth term of an arithmetic progression is half of its twelfth term. The first term is equal to

Worked solution (try it first)

The 6th term is $a + 5d$ and the 12th term is $a + 11d$ .
The 6th is half the 12th, so twice the 6th equals the 12th: $2a + 10d = a + 11d$ .
Take $a + 10d$ from both sides: $a = d$ .
The first term equals the common difference, option C.