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What formula represents the partial sum of the first n terms of the series 5 10 15 20 25?
The series given is an arithmetic progression consisting of 5 terms with a common difference of 5 and first term 5 → sum{n} = (n/2)(2×5 + (n - 1)×5) = n(5n + 5)/2 = 5n(n + 1)/2 As no terms have been given beyond the 5th term, and the series is not stated to be an arithmetic progression, the above formula only holds for n = 1, 2, ..., 5.
What is the sum of the first 15 multiples of 8?
Sum of the first 15 positive integers is 15*(15+1)/2 = 120 Sum of the first 15 multiples of 8 is 8*120 = 960
The fourth term of an AP is 15 and the sum of the first 5 terms is 55. Find the first term and the common difference?
x is the first term and d is the difference then x + 3d = 15 and sum of first five terms isx + (x+d) + (x+2d) + (x+3d) + (x+4d)so 5x + 10d = 55 ie x + 2d = 11As x + 3d = 15, d = 4 and x = 3,giving the five terms as 3, 7, 11, 15 and 19
What is the sum of the first fifteen odd numbers?
The sum of the first 15 odd numbers is 225.
What is the sum of the first five whole numbers?
The sum of the first five whole numbers is 10.
