Question

Find the sum of 2 5 8 17 up to 20 terms

Answer 1

$\sf{\pmb{CORRECT \; QUESTION:}}$

• Find the sum of AP of 2,5,8,17 up to 20 terms

$\purple {{{\sf ANSWER }}}$

Let :

$a = 2 \\ d = 3 \\ n = 20$

To Find :

$s_{n} = ?$

Now :

$s_{n} = \frac{n}{2} (2a + (n - 1)d) \\ \\ s_{n} = \frac{20}{2} (2(2) + 20 - 1)(3) \\ \\ s_{n} = 10(4 + 19)(3) \\ \\ s_{n} = 10(23)(3) \\ \\s_{n} = 10(69) \\ \\ \purple {{{\sf s_{n} = 690 }}}$