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What is the formula to find the sum of an arithmetic progression's first n terms?

55. What is the formula to find the sum of an arithmetic progression's first n terms?

1. (Sn) = (n/2) * [2a + (n+1)d]
2. (Sn) = (n/2) +[2a + (n-1)d]
3. (Sn) = (n*2) * [2a + (n-1)d]
4. (Sn) = (n/2) * [2a + (n-1)d]

Answer

The correct answer is: D) (Sn) = (n/2) * [2a + (n-1)d]

Explanation

The following formula can be used to calculate the sum of the first n terms of an arithmetic progression (AP):

Sum of first n terms (Sn) = (n/2) * [2a + (n-1)d]

Where:

• Sn is the sum of the arithmetic progression's first n terms.
• n is the number of terms in the progression.
• a is the first term of the progression.
• d is the common difference between consecutive terms.