Question

The sum of 15 terms of A.P.3,6,9
The sum of the 15 terms of A.P.3,6,9

Answer 1

Answer:

360

Step-by-step explanation:

since the formula for sum of n terms of an A.P. is

N/2 [ 2a + (n-1)d ]

where a = first term

N = no. of terms

d = common difference

here in the question, a = 3, d = 3, and N = 15.

=> sum = 15/2 [ 2*3 + (15 - 1)*3 ]

= 15/2 [6 + 14*3 ]

= 15/2 [ 6 + 42]

= 15/2 [ 48]

= 15 * 24

= 360