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There are 16 terms in an arithmetic progression (AP). The sum of the first 7 terms is 126, and the sum of the last 7 terms is 441.

Find the sum of the 10 terms after excluding the first and last term of the given AP.

Answer :

The sum of 10 terms after excluding from the first and last term of the given AP. is: 1055

How to find the sum of an arithmetic sequence?

The formula for the sum of n terms of an arithmetic sequence is:

Sₙ = ⁿ/₂[2a + (n - 1)d]

Where:

n is number of terms

a is first term

d is common difference

There are 16 terms in the sequence and as such:

S₇ = ⁷/₂[2a + (7 - 1)d] = 126

⁷/₂[2a + 6d] = 126

7a + 21d = 126 ------(1)

Total sum of the last 7 terms is 441. Thus:

a + 9d + a + 10d + a + 11d + a + 12d + a + 13d + a + 14d + a + 15d = 441

7a + 84d = 441 ----(2)

Subtract eq 1 from eq 2 to get:

63d = 315

d = 315/63

d = 5

7a + 21(5) = 126

7a + 105 = 126

7a = 21

a = 3

The 16th term is:

3 + 15(5) = 78

Thus, the next ten terms are:

83, 88, 93, 98, 103, 108, 113, 118, 123, 128

Total = 83 + 88 + 93 + 98 + 103 + 108 + 113 + 118 + 123 + 128

Total = 1055

Read more about Arithmetic Sequence at: https://brainly.com/question/6561461

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