Question

What is the sum of the first 20 terms of the series 3 + 14 + 25 + 25 + 36 +

Answer 1

Answer:

$S _{20} = 2150$

Step-by-step explanation:

$a _{1} = 3 \\ a _{2} = 14 \\ d = a _{2} - a_{1} = 14 - 3 = 11 \\ n = 20$

$S _{n} = \frac{n}{2} (2a + (n - 1)d) \\ \\ S _{20} = \frac{20}{2} (2(3) + (20 - 1) \times 11) \\ \\ S _{20} = 10 \times (6 + 19 \times 11) \\ S _{20} = 10 \times (6 + 209) \\ S _{20} = 10 \times 215 \\ S _{20} = 2150$

Answer 2

2150 is the correct answer