Question

sum of first 55 terms in an A.P. is 3300, find its 28th term

Answer 1

Answer:

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

Answer 2

Answer:

here's your answer

Step-by-step explanation:

First we find the first term and common difference between the A.P. by making the two equation.

Equation-1 {55}

S 55=n/2(2a+(n-1)d)

3300=55/2(2a+(55-1)d)

12=2a+54d

2(6)=2(a+27d)

a+27d=6

Equation-2 {28}

S 28=n/2(2a+(n-1) d)

S 28 = 28/2(2a+(28-1) d)

S 28= 28a+378d

now subtract both equation

27a+351d=6

3(9a+117d) = 3(2)

9a+117d= 2

now if we put any number in place of a we find the common difference

so if the a is 1 then the common difference is

9(1) +117d=2

d=-7/117 =0.05

If d is 0.05 then

a 28= 1+(28-1) (0.05)

a28 = 2.35

here's your answer

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