Question

Sum of first 55 terms of an A.P. is 3300. Then find its 28th term.​

Answer 1

Answer:

.. 28th term of A.P. is 60.

Step-by-step explanation:

For an A.P., let a be the first term and d be the common difference.

S_{55} = 3300

.. [Given]

e know that,

} = n/2 * [2a + (n - 1) * d]

55

:: S55 =

[2a + (55 - 1) d]

55 :: 300 = -[2a + 54d] 2

55 :: 3300 = x 2[a + 27d] 2

3300 = 55[a + 27d]

a + 27d = 3300/55

a + 27d = 60

..(i)

Now, t_{n} = a + (n - 1) * d

t_{28} = a + (28 - 1) * d

:: t_{28} = a + 27d

:: t_{28} = 60

..[From (i)]

.. 28t.. 28th term of A.P. is 60.h term of A.P. is 60.

Answer 2

Answer:

28th term of AP is 60

explanation:

Let a and d be the first term and common difference of the given AP respectively.

Given, S

55

=3300

⇒

2

55

[2a+(55−1)d]=3300

⇒55[a+27d]=3300

⇒a+27d=60

Hence, 28

th

term a

28

=a+27d=60