Question

18. Find the sum of 5 + 8 + 11 + ... to 10 terms using the formula,​

Answer 1

Answer:

Given AP: 5+ 8+ 11+........10 terms

here, a = 5 , n= 10 , d =3

10th term = a + (n - 1) d

= 5 + (10 -1) 3

= 5+ 9 (3)

=5+27

therefore, 10th term=32

sum of 10 terms = n/2 ( a+ 10th term )

=10/2 ( 5+32)

= 5 ( 37 )

=185

therefore, sum of the given terms is 185