Counting Principles, Permutations & Combinations Practice Set: NEB 12 Maths

Worked practice

Build the result from meaning, not memory

Counting principles build totals without listing every outcome. Permutations count ordered arrangements, combinations unordered selections, and restrictions must be handled before choosing a formula.

The governing relationship is nPr=n!/(n−r)! and nCr=n!/[r!(n−r)!], with nPr=r! nCr. Product and sum rules apply to sequential and alternative cases. Check the convention, geometry or boundary condition before calculation.

Independent practice ladder

1. Define the key physical quantities and give their SI units.
2. Draw and label the relevant wave, ray, mode or energy diagram.
3. Recalculate the worked example after changing one input by a factor of two.
4. Explain the result without equations.
5. Create a Nepal-relevant situation such as a classroom speaker, musical pipe, optical slit or thermal machine.
6. Compare two cases and predict the larger output before calculating.
7. Find and repair one deliberately wrong sign, node or unit.
8. Write a three-mark answer and a five-mark answer.

Answer protocol: diagram → known data → principle → symbolic equation → SI substitution → result → physical check. Using permutations for selections, double-counting identical objects, adding sequential choices instead of multiplying, or ignoring forbidden positions.

NEB answer method

Model → evidence → equation → check

First identify the system and what the question asks. Label the diagram, apparatus or reaction with SI quantities, then state the principle before selecting an equation. Solve symbolically where possible and check units, limiting cases and chemical or physical meaning.

Make the idea concrete in Nepal

Connect the model to a school laboratory, household technology, health, environment, energy or local material. The example should clarify the science rather than merely mention a place. Compare a prediction with an observation and record uncertainty.

Review the NEB Class 12 Mathematics revision roadmap and the complete Mathematics guide. For online or physical tuition, call 9846662070.

Frequently asked questions

Questions students ask about Counting Principles, Permutations and Combinations

References and next steps

Scope checked against CDC Nepal; concept support from an institutional reference and OpenStax Science. Continue with the Counting Principles, Permutations and Combinations cluster.