Question

What is the sum of first 5 terms of an AP whose 3rd term is 5?​

Answer 1

Answer:

S5=25

Step-by-step explanation:

Tn=a+(n-1)d

T3=a+(3-1)d

5=a+2d

a=5-2d ------------->eq 1

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

S5=5/2[2(5-2d)+(5-1)d]

=5/2[10-4d+4d]

=5/2×10

=25