Question

Find the sum of the first 30 positive multiples of 3.

Answer 1

arithmetic series

Answer 2

a = 3 d=3 n=30

Answer 3

i believe its 1395

Answer 4

not sure check just in case

Answer 5

jimmy is it right?

Answer 6

use Sn = n/2 [2a + (n-1)d]

Answer 7

ill check

Answer 8

i thought the equation is Sn = n/2(A1+An)

Answer 9

i guess its a variation

Answer 10

15 *( 6 + 29*3) = 15 * 93 = 1395

Answer 11

yep its was 1395

Answer 12

so jimmy
Sn = n/2(A1+An)
also works

Answer 13

its the one i was taught

Answer 14

faster to do

Answer 15

yes - when An = last term

Answer 16

yep