Number of terms from partial sums

An arithmetic progression has an even number of terms. The sum of the odd‑indexed terms is $24$, the sum of the even‑indexed terms is $30$, and the last term exceeds the first by $10\frac{1}{2}$. Find the total number of terms.

H. S. Hall & S. R. Knight, Higher Algebra (1891) · Ch. IV. Arithmetical Progression, Examples IV.b, No. 21