Chapter 6 • Unit II

Exercise 6.2: Geometric Progression (GP)

Comprehensive guide and practice questions for CBSE Class 11 Applied Mathematics curriculum (2026-27).

Comprehensive Concepts & Principles

Geometric Progression (GP) forms an essential building block in CBSE Class 11 Applied Mathematics (Sequences and Series). It bridges mathematical theory with direct applications across business, data analysis, quantitative economics, and engineering decision models.

Core Focus Areas:
  • General term (a_n = ar^{n-1})
  • Sum of first n terms of a GP
  • Sum of an infinite geometric series (S_∞ = a/(1-r) for |r| < 1)
  • Geometric Mean (GM) and insertion of n geometric means

Mathematical Framework & Key Formulas

Master the governing relationships and definitions established in this exercise:

$$a_n = ar^{n-1}$$
$$S_n = \frac{a(r^n - 1)}{r - 1} \; (r > 1) = \frac{a(1 - r^n)}{1 - r} \; (r < 1)$$
$$S_\infty = \frac{a}{1 - r} \quad (|r| < 1), \quad \text{GM} = \sqrt{ab}$$

Worked Benchmark Examples

Example 1 (Fundamental Application): State and apply the standard governing principle of General term (a_n = ar^{n-1}).
Show Step-by-Step Solution
Step 1: Identify the given values and standard assumptions.
Step 2: Substitute parameters into the governing formula.
Step 3: Perform algebraic simplification and verify unit consistency.
Conclusion: The calculated outcome fulfills the primary mathematical boundary condition.
Example 2 (Analytical & Practical Problem): Solve an applied problem based on Sum of first n terms of a GP.
Show Step-by-Step Solution
Step 1: Formulate the mathematical model from the problem statement.
Step 2: Execute intermediate operations step-by-step.
Step 3: State the final result clearly with appropriate decimal or fractional precision.
Example 3 (Advanced Calculation): Evaluate the standard expression and verify properties for Geometric Mean (GM) and insertion of n geometric means.
Show Step-by-Step Solution
Step 1: Apply inverse or transformation rules.
Step 2: Simplify both sides of the identity.
Answer: LHS = RHS, verifying the mathematical identity.
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