Question

The \( 10^{th} \) term and the \( 18^{th} \) term of an A.P. are \( 25 \) and \( 41 \) respectively. What is the first term \( a \)?

Options

• \( a = 9 \)

• \( a = 7 \)

• \( a = 25 \)

• \( a = 2 \)

Answer 1

From \( 8d = 16 \), \( d = 2 \). Substituting \( d = 2 \) into \( t_{10} = a + 9d = 25 \) gives \( a + 9(2) = 25 \), so \( a = 25 - 18 = 7 \).