Arithmetic Series (AQA A-Level Mathematics): Quizzes

Adding all terms in a sequence

$u_n = a + (n-1)d$

Sum of first $n$ terms

$S_n = \frac{n}{2}[2a + (n-1)d]$

$10,400$

$a + 2d = 72$

$S_n = \frac{n}{2}[a + l]$

Using $S_{59} - S_{21}$

$39$

$44$