Week 1 – My Arithmetic Sequence

5, 10, 15, 20, 25, …

$t_n$ = $t_1$ + (n – 1)d

$t_n$ = 5 + (n – 1)(5)

$t_n$ = 5 + 5n – 5

$t_n$ = 5n

$t_n$ = $t_1$ + (n – 1)d

$t_{50}$ = 5 + (50 – 1)(5)

$t_{50}$ = 5 + 245

$t_{50}$ = 250

$S_n$ = $\frac{n}{2}$ ( $t_1$ + $t_n$ )

$S_{50}$ = $\frac{50}{2}$ (5 + 250)

$S_{50}$ = 25(255)

$S_{50}$ = 6,375

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