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12 grade maths others

Two numbers are selected at random (without replacement) from the first six positive integers. Let X denote the larger of the two numbers obtained. Find the probability distribution of the random variable X and hence find the mean of the distribution.

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We are selecting two numbers at random without replacement from the first six positive integers: {1, 2, 3, 4, 5, 6}. Let X denote the larger of the two numbers chosen. Our goal is to find the probability distribution of X and then calculate its mean.

Step 1: List all possible pairs of numbers
The total number of ways to select 2 numbers from a set of 6 numbers is given by the combination formula: C(n, r) = n! / [r!(n - r)!] For n = 6 and r = 2, we have: C(6, 2) = 6! / (2!(6 - 2)!) = (6 × 5) / 2 = 15

So, there are 15 possible pairs of numbers. These pairs are: (1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (2, 3), (2, 4), (2, 5), (2, 6), (3, 4), (3, 5), (3, 6), (4, 5), (4, 6), (5, 6)

Step 2: Identify the values of X
For each pair, the larger of the two numbers is X:

For (1, 2), X = 2
For (1, 3), X = 3
For (1, 4), X = 4
For (1, 5), X = 5
For (1, 6), X = 6
For (2, 3), X = 3
For (2, 4), X = 4
For (2, 5), X = 5
For (2, 6), X = 6
For (3, 4), X = 4
For (3, 5), X = 5
For (3, 6), X = 6
For (4, 5), X = 5
For (4, 6), X = 6
For (5, 6), X = 6
Thus, X can take the values 2, 3, 4, 5, and 6.

Step 3: Find the probability distribution of X
To find the probability distribution of X, we count how many times each value of X occurs and divide by the total number of outcomes (15).

X = 2 occurs 1 time: (1, 2)
X = 3 occurs 2 times: (1, 3), (2, 3)
X = 4 occurs 3 times: (1, 4), (2, 4), (3, 4)
X = 5 occurs 4 times: (1, 5), (2, 5), (3, 5), (4, 5)
X = 6 occurs 5 times: (1, 6), (2, 6), (3, 6), (4, 6), (5, 6)
Now, we calculate the probabilities:

P(X = 2) = 1/15
P(X = 3) = 2/15
P(X = 4) = 3/15
P(X = 5) = 4/15
P(X = 6) = 5/15
Step 4: Find the mean of the distribution
The mean of the distribution is given by the expected value of X, which is the sum of each possible value of X weighted by its probability:

E(X) = Σ [x * P(X = x)]

E(X) = (2 * 1/15) + (3 * 2/15) + (4 * 3/15) + (5 * 4/15) + (6 * 5/15)

E(X) = (2/15) + (6/15) + (12/15) + (20/15) + (30/15)

E(X) = (2 + 6 + 12 + 20 + 30) / 15

E(X) = 70 / 15

E(X) = 14/3 ≈ 4.67

Final Answer:
The probability distribution of X is:

P(X = 2) = 1/15
P(X = 3) = 2/15
P(X = 4) = 3/15
P(X = 5) = 4/15
P(X = 6) = 5/15
The mean of the distribution is 14/3 ≈ 4.67.


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Step 1: Building Number Understanding

Before children start solving sums, they must first understand numbers clearly.

Young learners should become familiar with:

  • Counting numbers

  • Recognising numbers

  • Understanding the value of numbers

Teachers often use simple activities such as counting objects, toys, or fruits to help children understand numbers.

For example, parents can ask questions like:

  • How many apples are on the table?

  • Can you count the pencils in your bag?

These small activities help children connect numbers with real objects.

Step 2: Learning Addition (Basic Sums)

Addition is usually the first mathematical operation children learn.

Addition means combining numbers together.

For example:

2 + 3 = 5

Teachers often teach addition using objects.

Example:

If a child has 2 pencils and receives 3 more pencils, the total becomes 5 pencils.

Using objects makes the concept easier to understand.

Simple addition practice

Parents can practice with children using:

  • fingers

  • small toys

  • beads

  • fruits

Once children understand the concept, they can move on to written sums.

Step 3: Understanding Subtraction

Subtraction means taking away from a number.

Example:

5 − 2 = 3

Teachers often explain subtraction using real situations.

Example:

If a child has 5 chocolates and gives 2 chocolates to a friend, how many chocolates remain?

This approach helps children understand subtraction more clearly.

Parents can encourage children to think about subtraction in everyday situations.

Step 4: Learning Multiplication

Multiplication is often introduced after children become comfortable with addition.

Multiplication means repeated addition.

Example:

3 × 4 means adding 4 three times.

4 + 4 + 4 = 12

Teachers often explain multiplication using groups.

Example:

If there are 3 groups of 4 apples, the total number of apples is 12.

Using pictures or objects helps children visualise multiplication easily.

Step 5: Multiplication Tables (Learning Vaaipaadu)

In Tamil education systems, multiplication tables are often called “vaaipaadu”.

Memorising tables helps children solve multiplication problems faster.

Common tables include:

2 × 1 = 2
2 × 2 = 4
2 × 3 = 6

Tables usually begin from 2 and go up to 10 or 12.

Teachers often encourage children to practice tables through:

  • repetition

  • rhythm or songs

  • daily practice

Parents can make table learning interesting by asking questions during daily activities.

For example:

If one box contains 5 chocolates, how many chocolates are there in 3 boxes?

These small questions strengthen table knowledge.

Step 6: Understanding Division

Division is the opposite of multiplication. It means sharing or splitting numbers equally.

Example:

12 ÷ 3 = 4

Teachers explain division using sharing examples.

Example:

If 12 sweets are shared equally among 3 children, each child receives 4 sweets.

This helps children understand the concept of division clearly.

Making Basic Maths Skills Practice Fun at Home

Mathematics should not feel like a stressful subject for children. Parents can help children enjoy maths through simple activities.

Some useful methods include:

Asking children to count objects around the house

Practicing tables during daily routines

Solving small sums during shopping or cooking

Playing number-based games

When maths becomes part of daily life, children learn faster.

Encouraging Confidence in Maths

Some children feel nervous about mathematics because they fear making mistakes.

Teachers usually encourage students to see mistakes as part of learning.

Parents can support children by:

  • appreciating their effort

  • encouraging them to try again

  • avoiding comparison with other students

Confidence grows when children feel supported.

Balancing Practice and Understanding

Memorising formulas or tables alone is not enough. Children should also understand the logic behind the calculations.

For example, a child who understands multiplication as repeated addition will find division easier to learn.

Teachers often recommend a balanced approach:

  • understanding concepts

     

  • regular practice

     

  • problem-solving exercises

This combination helps children build strong mathematical skills.

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