Question

Question 1 Given the arithmetic series: 20 + 27 +34 + 41 + ... find the sum to 11 terms.

pls show solution ;-;​

Answer 1

Answer:

682.

Explanation:

Since the given sequence (20, 27, 34, 41...) can be described as 7n+20, you can just test every value of n and sum it up, or you can use a little trick:

You can sum just the simple part (11 + 10 + 9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1) which results in 66.

You can use the following expression (modifying the original one):

$7(66)+20(11)$

Which gives 462 + 220, which is equal to 682.

This could be found with the following sum as well:$27+34+41+48+55+62+69+76+83+90+97$