Arithmetic Progression Calculator
About Arithmetic Progression
An arithmetic progression (AP) or arithmetic sequence is a sequence of numbers such that the difference between the consecutive terms is constant. For instance, the sequence 5, 7, 9, 11, 13, ... is an arithmetic progression with a common difference of 2.
Formulas
General term (nth term): an = a1 + (n - 1)d
Sum of n terms: Sn = n/2[2a1 + (n - 1)d] = n/2[a1 + an]
Common difference: d = (an - a1) / (n - 1)
First term: a1 = an - (n - 1)d
Number of terms: n = (an - a1) / d + 1
Examples
Example 1: Find the 10th term of the arithmetic progression 2, 5, 8, 11, ...
First term (a1) = 2, Common difference (d) = 3, n = 10
Using the formula: an = a1 + (n - 1)d
a10 = 2 + (10 - 1) × 3 = 2 + 9 × 3 = 2 + 27 = 29
Example 2: Find the sum of the first 15 terms of the AP: 3, 8, 13, 18, ...
First term (a1) = 3, Common difference (d) = 5, n = 15
Using the formula: Sn = n/2[2a1 + (n - 1)d]
S15 = 15/2[2 × 3 + (15 - 1) × 5] = 15/2[6 + 14 × 5] = 15/2[6 + 70] = 15/2 × 76 = 570