Solving Summation Notation

A summation notation (Σ) is used for sum the numbers or quantities indicated. We can sum all types of numbers such as real, integer, complex, rational numbers using sigma notation. Summation notation is also called as sigma notation. Using summation notation we can solve the problems easily. Summation a concise and convenient way of writing long sums.


I like to share this Fractional Notation with you all through my article.

Solving Summation Notation – Solving Example Problems

Example 1: Find the sum for the given expression and explain the terms of summation notation;

7

∑ (n + 1)3 =?

n=1

Solution:

7

∑ (n + 1)3 =?

n=1

Lower Bound: ‘n’ is the lower bound of the summation notation.

Upper Bound:  ‘7’ is the upper bound of the summation notation.

Formula: (n + 1)3 is the formula to describe the each term of the summation notation.

Start: n = 1, here 1 is indicating the first number of the terms of summation notation. Usually value of start is zero (0) or one (1).

End: 7 is indicating the last umber of the terms of the summation notation.

Index Variable: Index variable ‘n’ is used to labeled each term of summation notation.

7

∑ (n + 1)3 = 8 + 27 + 64 + 125 + 216 + 343 + 512 = 1295

n=1

7

Therefore, ∑ i3 = 1295

i=1

Example 2: Solve and find the sum for the given expression;

6

∑ 3(n + n2) =?

n=1

Solution:

6

∑ 3(n + n2) =?

n=1

Formula: 3(n + n2), starting term: 1, end term: 6, and index variable: n

6

∑ 3(n + n2) / n = 3(1 + 12) + 3(2 + 22) + 3(3 + 32) + 3(4 + 42) + 3(5 + 52) + 3(6 + 62)

i=1


= 3(1 + 1) + 3(2 + 4) + 3(3 + 9) + 3(4 + 16) + 3(5 + 25) + 3(6 + 36)

= 3(2) + 3(6) + 3(12) + 3(20) + 3(30) + 3(42)

= 6 + 18 + 36 + 60 + 90 + 126

= 336

6

Therefore, ∑ 3(n + n2) = 336

i=1

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Example 3: Solve and find the sum for the given expression;

6

∑ n(2n + 1) / 2 =?

n=1

Solution:

6

∑ n(2n + 1) / 2 =?

n=1

Formula: n(2n + 1) / 2, starting term: 1, end term: 6, and index variable: n

6

∑ n(2n + 1) / 2 = (1(2(1) + 1) / 2) + (2(2(2) + 1) / 2) + (3(2(3) + 1) / 2) + (4(2(4) + 1) / 2)

n=1  + (5(2(5) + 1) / 2) + (6(2(6) + 1) / 2)


= (1(3) / 2) + (2(5) / 2) + (3(7) / 2) + (4(9) / 2) + (5(11) / 2) + (6(13) / 2)

= (3 / 2) + (10 / 2) + (21 / 2) + (36 / 2) + (55 / 2) + (78 / 2)

= 1.5 + 5 + 10.5 + 18 + 27.5 + 39

= 101.5

6

Therefore, ∑ n(2n + 1) / 2 = 101.5

n=1
Solving Summation Notation – Solving Practice Problems

Problem 1: Solve and calculate the sum for the given expression;

5

∑ n2(n) =?

n=1

Answer: 225

Problem 2: Solve and calculate the sum for the given expression;

5

∑ (2n + 2) / n =?

n=1

Answer: 14.57