Question

Find the sum of the first 31 terms of an A.P whose nth term is given by 3 + 2/3 n .

Answer 1

Answer:

1271 / 3

Step-by-step explanation:

Since nth term is 3 + ( 2 / 3 ) n,

a1 = 3 + ( 2 / 3 ) 1 = 3 + 2 / 3 = 11 / 3

a2 = 3 + ( 2 / 3 ) 2 = 3 + 4 / 3 = 13 / 3

a3 = 3 + ( 2 / 3 ) 3 = 3 + 6 / 3 = 15 / 3 = 5

Hence,

a = 11 / 3, d = 13 / 3 - 11 / 3 = 15 / 3 - 13 / 3 = 2 /3

Sum of 31 terms:

[ 31 / 2 ] [ 2 ( 11 / 3 ) + ( 31 - 1 ) ( 2 / 3 )]

= [ 31 / 2] [ 22 / 3 + ( 30 ) ( 2 / 3 ) ]

= [ 31 / 2] [ 22 / 3 + 20 ]

= [ 31 / 2 ] [ 82 / 3 ]

= 1271 / 3

Answer 2

hope it will help uh ..
nd plz mark as brainliest ..☺☺