Question

Find the sum of 15th term 3+6+9

Answer 1

Answer:

SUM OF 15 TERMS = 360.

Step-by-step explanation:

$ap \: \: \: \: \: \: 3 + 6 + 9 + .... \\ \\ sum \: of \: 15 \: terms = \frac{15}{2} (2(3) + (14)( 3)) \\ \\ = \frac{15}{2} (6 +42) \\ \\ = \frac{15}{2} ( 48) \\ \\ = 15 \times 24 \\ \\ = 360.$

Answer 2

Answer:

nth term of arthimetic progression is a+(n-1) d

here, a=3,d=3, n=15

=a+(n-1) d

=3+(15-1) 3

=3+52

=45