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12 grade maths others

A tank with rectangular base and rectangular sides open at the top is to be constructed so that its depth is 3 m and volume is 75 m³. If building of tank costs Rs. 100 per square metre for the base and Rs. 50 per square metres for the sides, find the cost of least expensive tank.

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11 Months agoGrade
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ApprovedApproved Tutor Answer11 Months ago

To find the least expensive tank with a given volume and dimensions, we start by defining the variables and equations based on the problem's requirements.

Defining Variables

Let:

  • l = length of the base (in meters)
  • w = width of the base (in meters)
  • h = height of the tank = 3 m

Volume Equation

The volume of the tank is given by:

Volume = length × width × height

Substituting the known height:

75 = l × w × 3

This simplifies to:

l × w = 25

Cost Calculation

The cost of constructing the tank involves two parts: the base and the sides.

  • Cost of the base = 100 × (l × w)
  • Cost of the sides = 50 × (2h(l + w))

Substituting the height:

Cost of sides = 50 × (2 × 3 × (l + w)) = 300(l + w)

Total Cost Function

The total cost (C) can be expressed as:

C = 100lw + 300(l + w)

Using the relationship lw = 25, we can express w in terms of l:

w = 25/l

Substituting for Cost

Now, substitute w into the cost function:

C = 100(25) + 300(l + 25/l)

This simplifies to:

C = 2500 + 300l + 7500/l

Finding the Minimum Cost

To minimize the cost, we take the derivative of C with respect to l and set it to zero:

dC/dl = 300 - 7500/l² = 0

Solving for l gives:

300l² = 7500

l² = 25

l = 5 m

Calculating Width

Now, substituting back to find w:

w = 25/l = 25/5 = 5 m

Final Cost Calculation

Now we can calculate the total cost:

C = 2500 + 300(5) + 7500/5

C = 2500 + 1500 + 1500 = 5500

Conclusion

The cost of the least expensive tank is Rs. 5500.


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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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Grade 1212 grade maths others

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