Question

What is the sum of the first 15 terms of an AP. 3,5.5,8,10.5,13........

Answer 1

Step-by-step explanation:

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

a=3 d=2.5 n=15

Substituting,

Sn=15/2[2*3+(15-1)*2.5]

=15/2(6+14*2.5)

=15/2(6+35)

=15/2(41)

=7.5*41

=307.5

Answer 2

Answer:

Given data:

a=3, n=15,d=2.5

Step-by-step explanation:

Tn = a+(n-1)d

T(15)=3+(15-1)2.5

T(15)=3+14*2.5

=3+35

T(15)=38