Question

In the formula \( t_{10} = a + 9d = 25 \), which value is used in place of \( (n - 1) \)?

Options

• \( 8 \)

• \( 10 \)

• \( 25 \)

• \( 9 \)

Answer 1

Using \( t_{n} = a + (n - 1)d \) with \( n = 10 \) gives \( t_{10} = a + (10 - 1)d = a + 9d \). Hence \( (n - 1) = 9 \) common differences are added to the first term.