Question

If the 10th term of an A.P is 3 8 and the 16th term is 7 4. Find the sum of first 20 terms of A.P. Please solve it fast ​

Answer 1

Step-by-step explanation:

a=8,a

n

=33,S

n

=123

a

n

=a+(n−1)d

⇒33=8+(n−1)d

⇒(n−1)d=25

S

n

=

2

n

[2a+(n−1)d]

123=

2

n

[2×8+25]

246=n[16+25]

⇒n=

41

246

∴n=6

(n−1)d=25

(6−1)d=25

∴d=5