Arithmetic Progression (AP) has constant difference d between consecutive terms. General term: aₙ = a + (n-1)d, where a = first term, d = common difference. Example: 3, 7, 11, 15, ... has a=3, d=4. So a₅ = 3 + 4(4) = 19. Identifying AP: Check if differences are constant. Finding d: d = a₂ - a₁. Finding nth term: aₙ = a + (n-1)d. Solving MCQs: (1) Find d from consecutive terms; (2) Use formula for specific term; (3) Verify pattern. Shortcut: Memorize formula. Practice: Rearrange formula to find a, d, or n. Exam tip: Distinguish AP from other sequences (geometric, Fibonacci). Always state a and d explicitly.