Question

Sum of First 55 term of A.P. is 3300. Find 28th term.

Answer 1

Given: S55 = 3300 where n = 55

Now, By using sum of nth term of an A.P. we will find it’s sum

Where, n = no. of terms

a = first term

d = common difference

Sn = sum of n terms

Thus, on substituting the given value in formula we get,

⇒ 3300 = 55 × [ a + 27d]

⇒ a + 27d = 60 ……(1)

We need to find value of 28th term i.e t28

Now, By using nth term of an A.P. formula

tn = a + (n – 1)d

where n = no. of terms

a = first term

d = common difference

tn = nth terms

we can find value of t28 by substituting all the value in formula we get,

⇒ t28 = a + (28 – 1) d

⇒ t28 = a + 27 d

From eq. (1) we get,

⇒ t28 = a + 27 d = 60

⇒ t28 = 60