GANITA MANJARI · GRADE 9 · PART I · CHAPTER 7
Visual Lessons
Think first. Use AI purposefully. Verify always.
CHANCE — Uncertainty and random experiments
Predict one trial
Local seeded simulation of independent fair coin tosses. These are generated observations, not textbook experimental data. A fixed seed reproduces the same sequence.
Trials: 0 · Heads: 0 · Tails: 0
No trials yet: observed relative frequency is not defined.
Last 0 results: None yet
Long-run relative frequency tends towards the model value; exact equality at a set number of trials is not guaranteed.
SCALE — Probability from 0 to 1
Locate the chance
Impossible
Even chance1
Certain
Even chance of purple versus not purple. Each card is equally selectable. The complementary event has 3 favourable cards.
OBSERVE — Experimental probability and relative frequency
Record, count, compare
Local seeded simulation of independent fair coin tosses. These are generated observations, not textbook experimental data. A fixed seed reproduces the same sequence.
Trials: 0 · Heads: 0 · Tails: 0
No trials yet: observed relative frequency is not defined.
Last 0 results: None yet
Long-run relative frequency tends towards the model value; exact equality at a set number of trials is not guaranteed.
EXPECT — Theoretical probability and equal likelihood
Select an event
S = {1,2,3,4,5,6}. E = {2, 4, 6}. A check mark identifies each favourable outcome.
This counting rule applies because the six faces are equally likely. A biased die requires its outcome probabilities instead.
COMPARE — Experimental versus theoretical probability
A longer run, not a guarantee
Local seeded simulation of independent fair coin tosses. These are generated observations, not textbook experimental data. A fixed seed reproduces the same sequence.
Trials: 0 · Heads: 0 · Tails: 0
No trials yet: observed relative frequency is not defined.
Last 0 results: None yet
Long-run relative frequency tends towards the model value; exact equality at a set number of trials is not guaranteed.
SAMPLE — Evidence, samples and representativeness
Who is included in the sample?
Illustrative population, not survey data: 100 people in equal groups A and B. In A, 40 of 50 prefer mango; in B, 10 of 50 do. The population share is 50%.
SPACE — Sample spaces, n(S) and events
Build a complete sample space
n(S) = 4. Every possible recorded outcome appears once.
Uniform probabilities require fair independent coin tosses and, for cards, uniform independent selection.
BRANCH — Trees and multi-step experiments
Follow the conditional branches
- ↳ Second: H ·
Outcome: HH - ↳ Second: T ·
Outcome: HT
- ↳ Second: H ·
Outcome: TH - ↳ Second: T ·
Outcome: TT
Multiply conditional probabilities along a path. Add disjoint path probabilities for a larger event. At every possible node, the outgoing probabilities sum to 1.
REASON — Fairness, dependence and careful conclusions
Is the opposite result due?
Suppose the past six results were H H H H H H. For independent fair tosses, predict the next tail probability.
Fresh tosses: 0. Latest simulated result: not started. These fresh trials are not forced to offset the hypothetical history.
Change the replacement rule
- ↳ Second: 2 ·
Outcome: 1, 2 - ↳ Second: 3 ·
Outcome: 1, 3 - ↳ Second: 4 ·
Outcome: 1, 4
- ↳ Second: 1 ·
Outcome: 2, 1 - ↳ Second: 3 ·
Outcome: 2, 3 - ↳ Second: 4 ·
Outcome: 2, 4
- ↳ Second: 1 ·
Outcome: 3, 1 - ↳ Second: 2 ·
Outcome: 3, 2 - ↳ Second: 4 ·
Outcome: 3, 4
- ↳ Second: 1 ·
Outcome: 4, 1 - ↳ Second: 2 ·
Outcome: 4, 2 - ↳ Second: 3 ·
Outcome: 4, 3
n(S) = 12. 4 × 3 = 12; the four repeated-label pairs are excluded.
Each pair has probability under uniform selection at each draw.
Uniform landing and area
Assume uniform landing over the rectangle. Each local simulated point uses uniform horizontal and vertical coordinates. Boundary conventions do not change the continuous-area probability.
Area of circle ÷ area of rectangle: () ÷ 6. Without uniform landing, this ratio is not justified.
