Arithmetic Progression, Geometric Progression and Harmonic Progression are interrelated concepts and they are also one of the most difficult topics in Quantitative Aptitude section of Common Admission Test, CAT. We will discuss them one by one.
Arithmetic Progression (AP)
The progression of the form: a, a + d, a + 2d, a + 3d … is known as an AP with first term = a,and common difference = d.
In an AP a, a + d, a + 2d, a + 3d, …, we have:
(i) nth term, T n = a + (n – 1)d
(ii) Sum to n terms, where l is the last term.
(iii) If a, b, c are in AP, then b is called with arithmetic mean (AM) between a andc. In this case, b = (a + c).