Answer:
The sum =105
Step-by-step explanation:
It is given that, finite sequence 3, 7, 11, ..., 27.
Points to remember
1). For a finite sequence sum of n term is given by
Sum = n/2[first term + last term]
2). nth term of of an AP
tₙ = a + (n - 1)d
Where a - First term
d - common difference
To find the number of terms in the given sequence
Here a = 3 and d = 7 - 3 = 4
tₙ = a + (n - 1)d
27 = 3 + (n - 1)*4
4(n -1) = 27 - 3 = 24
n - 1 = 24/4 = 6
n = 6 +1 =7
To find the sum
Sum = n/2[first term + last term]
= 7/2[3 + 27]
= 7/2[30] = 7 * 15
= 105
