Question

. If the second term and the fourth term of an
A.P. are 12 and 20 respectively then find the Sum of first 25 terms
​

Answer 1

Answer:1200

Step-by-step explanation:

2nd term = 12

a+d=12        =>1

4th term = 20

a+3d=20      =>2

Subtract 1 from 2

a+3d=20

a+d=12

---------------

2d=8

d=4

a+d=12

a+4=12

a=8

Sum of first 25 terms

25th term = a+24d

=8+96

=104

Sn=n/2(a+an)

=25/2*(104+8)

=25/2*112

=1400