Question

Q. 8. Find the Sum of A. P. 1, 4, 7....... up to 20 terms​

Answer 1

Answer:

590

Step-by-step explanation:

Answer 2

Step-by-step explanation:

$= >S _{20} = \frac{20}{2} (2 \times 1 + 19 \times 3) \ \\ \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = 10(2 + 57) \\ \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = 10 \times 59 \\ \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = 590$