Question

The 4 term of an ap is 10and its 11 term is one more than 3 times its 4 term . Find the sum of first 209 terms

Answer 1

hope it will help u

plzz mark as brainlist

Answer 2

Answer:

65417

Step-by-step explanation:

Let say first term = a

Common difference = d

nth Term = a + (n-1)d

4th term = a + 3d

a + 3d = 10   - eq 1

11th Term = a + 10d

11 term is one more than 3 times its 4 term

a + 10d = 3(10) + 1

=> a + 10d = 31    - eq 2

eq 2 - eq 1

=> 7d = 21

=> d = 3

a + 3d = 10

=> a + 9 = 10

=> a = 1

AP  1 , 4 , 7 , 10

Sn = (n/2)(a + a +(n-1)d)

Sum of 209 terms = (209/2) (1 + 1 + 208*3)

=(209/2)(2 + 624)

= (209/2)(626)

= 209 * 313

=  65417