Question

Sum of first 55 term is an
a.P is 3300 find its 28

Answer 1

Answer:

60 is the answer

Step-by-step explanation:

Sum = $\frac{n}{2} {2a + (n-1)d}$

where n = no. of terms  

a = first term

d = common difference

here n = 55

sum = 3300

use the above formula and we get

2a + 54d = 120   -------------- (1)

for 28 term

we have a + 27d  ----------------(2)

if we divide the equation (1)    by 2  

it gives us equation (2)

which we want

so a + 27d = 60

Hope it helps!!

Thanks

Answer 2

Answer:-

$\boxed{ \bf{t_{28} = 60}}$

Step - by - step explanation :-

To find :-

Find 28th term of the given AP.

Given :-

55th term is 3300.

Solution:-

Let first term of this AP is "a"

Common difference is "d"

According to the question-

$\: \bf{s_{55} = 3300} \\ \\ \bf{ \frac{55}{2} \bigg(2a + (55 - 1)d \bigg) = 3300} \\ \\ \bf{\frac{55}{2} \bigg(2a + 54d \bigg) = 3300} \\ \\ \bf{ 55(a + 27d) = 3300} \\ \\ \bf{a + 27d \: = 60 }\: \: \: ......(1)$

And also ,

We know that,

$\bf{t_{28} \: = a \: + (28 - 1)d} \\ \\ \bf{ t_{28} \: = a + 27d \: } \: ......(2)$

On comparing eq (1) and (2)

We get,

$\boxed{ \red{\bf{t_{28} = 60}}}$

Hope it helps you.