arithmetic sequence

Question

find the sum of the first 30 terms of the arithmetic sequence 6,11,16,21......

 

Answer 1

Arihemetic sequence S n = n/2[2a+(n-1)d]

Here d is common difference, a is first term

d = t2-t1 = 11-6 = 5

 a = 6,d = 5

and n =30

S 30 =30/2(2*6+(30-1)5 )

= 15(12-145)

= 15*-133

= 1995

Comments

Sum of first 30 termes in the sequence = 2355

Answer 2

Arihemetic sequence S n = n/2[2a+(n-1)d]

Here d is common difference, a is first term

d = t2-t1 = 11-6 = 5

 a = 6,d = 5

and n =30

S 30 =30/2(2*6+(30-1)5 )

= 15(12+145)

= 15*157

= 2355