CBSE MATHEMATICS • SELECTED CENTRAL & STATE COMPETITIVE EXAMS
AIMSSchool of MathematicsAim through AIMS

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.

Read the full lesson →

SCALE — Probability from 0 to 1

Locate the chance

0
Impossible
12
Even chance
1
Certain
P(purple)=36

Even chance of purple versus not purple. Each card is equally selectable. The complementary event has 3 favourable cards.

Read the full lesson →

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.

Read the full lesson →

EXPECT — Theoretical probability and equal likelihood

Select an event

12 ✓34 ✓56 ✓

S = {1,2,3,4,5,6}. E = {2, 4, 6}. A check mark identifies each favourable outcome.

P(E)=36

This counting rule applies because the six faces are equally likely. A biased die requires its outcome probabilities instead.

Read the full lesson →

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.

Read the full lesson →

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%.

Read the full lesson →

SPACE — Sample spaces, n(S) and events

Build a complete sample space

HHHTTHTT

n(S) = 4. Every possible recorded outcome appears once.

Uniform probabilities require fair independent coin tosses and, for cards, uniform independent selection.

Read the full lesson →

BRANCH — Trees and multi-step experiments

Follow the conditional branches

Two independent fair tosses · independent trials. Read each route from Start to its final outcome.
Start
First: H · 12
  • ↳ Second: H · 12
    Outcome: HH
  • ↳ Second: T · 12
    Outcome: HT
First: T · 12
  • ↳ Second: H · 12
    Outcome: TH
  • ↳ Second: T · 12
    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.

Read the full lesson →

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

Four equally selectable numbered balls · without replacement. Read each route from Start to its final outcome.
Start
First: 1 · 14
  • ↳ Second: 2 · 13
    Outcome: 1, 2
  • ↳ Second: 3 · 13
    Outcome: 1, 3
  • ↳ Second: 4 · 13
    Outcome: 1, 4
First: 2 · 14
  • ↳ Second: 1 · 13
    Outcome: 2, 1
  • ↳ Second: 3 · 13
    Outcome: 2, 3
  • ↳ Second: 4 · 13
    Outcome: 2, 4
First: 3 · 14
  • ↳ Second: 1 · 13
    Outcome: 3, 1
  • ↳ Second: 2 · 13
    Outcome: 3, 2
  • ↳ Second: 4 · 13
    Outcome: 3, 4
First: 4 · 14
  • ↳ Second: 1 · 13
    Outcome: 4, 1
  • ↳ Second: 2 · 13
    Outcome: 4, 2
  • ↳ Second: 3 · 13
    Outcome: 4, 3
(1,2)(1,3)(1,4)(2,1)(2,3)(2,4)(3,1)(3,2)(3,4)(4,1)(4,2)(4,3)

n(S) = 12. 4 × 3 = 12; the four repeated-label pairs are excluded.

Each pair has probability 112 under uniform selection at each draw.

Uniform landing and area

Rectangle: 3 m × 2 m. Dashed diameter: 1 m; radius: 0.5 m. The circle is wholly inside the rectangle.

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.

P=π24≈0.131

Area of circle ÷ area of rectangle: (π4) ÷ 6. Without uniform landing, this ratio is not justified.

Read the full lesson →