Question

The fourth term of an Ap is 10. If eleventh term is one more three times of the fourth term find the sum of its 25 terms. ​

Answer 1

Answer:

this is ur correct answer

Step-by-step explanation:

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u r in 10 right

Answer 2

Step-by-step explanation:

So, as a 3d = 10 --1

Substitute n = 11

a11 = a + (11-1)d

a11 a 10d

Now we are given that 11th term is one more three times of the fourth term

So, a11 - 3a4 + 1

So, a 10d=3(10) +1

a10d 31 --2

Subtract 1 form 2

a10da4d 31 10

6d=21

So, d = 21/6 =3.5

Substitute value of d in 1

a + 3(3.5) = 10

a 10.5 10 a = -0.5

Formula of sum of first n terms = Sn (2a + (n − 1)d) =Substitute n = 25

So, S25 = 25 (2(-0.5) + (25 − 1)3.5)

S25 = 1037.5

thus the sum of 25 terms is 1037.5