NEB Class 12 • Mathematics • Probability • Concept Guide

Conditional Probability & Combinatorial Probability: NEB Class 12 Maths Guide

Master Conditional Probability and Combinatorial Probability through clear concepts, representations, a reliable answer method and exam-focused practice.

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Concepts · Worked reasoning · NEB practice

Quick answer: Conditional probability updates a sample space after information is known. Combinatorial probability counts favorable and total outcomes carefully, while Bayes-style reasoning reverses conditions using base rates.

Core concept

What Conditional Probability and Combinatorial Probability means physically

Conditional probability updates a sample space after information is known. Combinatorial probability counts favorable and total outcomes carefully, while Bayes-style reasoning reverses conditions using base rates.

P(A|B)=P(A∩B)/P(B); P(A∩B)=P(A|B)P(B); independence means P(A|B)=P(A).

The institutional reference gives the wider physical model; the CDC curriculum determines the NEB boundary.

Worked checkpoint with interpretation

From a deck, given that a card is a face card, P(king|face)=4/12=1/3.

Do not stop at the number. State what the sign, ratio, spacing, frequency or direction means. A common error is Confusing P(A|B) with P(B|A), cancelling without conditioning the sample space, assuming independence, or counting ordered outcomes as unordered.

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.

Stage	Question	Evidence
Model	What is idealised?	Assumption stated
Representation	Which diagram fits?	Labels or balanced equation
Calculation	Which relation follows?	Symbols then SI values
Evaluation	Does it make sense?	Unit, sign and trend check

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.

Questions students ask about Conditional Probability and Combinatorial Probability

What is the central idea of Conditional Probability and Combinatorial Probability?

Which equation should I remember?

P(A|B)=P(A∩B)/P(B); P(A∩B)=P(A|B)P(B); independence means P(A|B)=P(A).

How should I begin a numerical?

Draw the situation, list known quantities in SI units, choose the governing relation symbolically, substitute once and finish with a unit and reasonableness check.

What is a common exam mistake?

Confusing P(A|B) with P(B|A), cancelling without conditioning the sample space, assuming independence, or counting ordered outcomes as unordered.

How can I practise this topic?

Alternate one concept explanation, one diagram and two numericals. Revisit errors after a day instead of only rereading the solution.

Where can I get tuition support?

For online or physical KTM Tuition classes, call 9846662070. After Grade 12, the MKS Education panel below gives preparation and pre-counselling contacts.

Frequently asked questions

References and next steps

Scope checked against CDC Nepal; concept support from an institutional reference and OpenStax Science. Continue with the Conditional Probability and Combinatorial Probability cluster.

NEB +2 tuition support

Ask about online or physical tuition

For focused Class 11 and Class 12 subject tuition, lesson clarification, worked-example practice and exam preparation, call 9846662070. Class mode, timetable, teacher availability and fees should be confirmed directly before enrolment.

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