🌱 What is this chapter about?
In this chapter, we learn a new and smart way to write maths.
Instead of writing long sentences again and again, we use letters to represent numbers.
This makes maths short, clear, and easy.
This idea is called algebra.
🔤 What are Letter-Numbers?
Sometimes, we do not know the exact number.
So we use a letter to represent that number.
Example:
Let a = Aftab’s age
Let s = Shabnam’s age
Letters like a, b, x, y that stand for numbers are called letter-number.
👦👧 Example 1: Age Problem (Very Easy)
Shabnam is 3 years older than Aftab.
If Aftab’s age = a,
then Shabnam’s age = a + 3
👉 If a = 10, then
Shabnam’s age = 10 + 3 = 13
👉 If a = 23, then
Shabnam’s age = 23 + 3 = 26
So we write:
s = a + 3
This is called an algebraic expression.
🧩 Example 2: Matchstick Pattern
Each L shape needs 2 matchsticks.
5 L shapes → 5 × 2 matchsticks
10 L shapes → 10 × 2 matchsticks
Let:
n = number of L shapes
Then:
Number of matchsticks = 2n
Just replace n with the number you want.
🛒 Example 3: Shopping Problem
Price:
1 coconut = ₹35
1 kg jaggery = ₹60
Let:
c = number of coconuts
j = kg of jaggery
Cost of coconuts = 35c
Cost of jaggery = 60j
Total cost =
35c + 60j
This single expression works for any quantity.
📐 Example 4: Perimeter of a Square
A square has 4 equal sides.
Let:
q = length of one side
Perimeter =
4q
If q = 7 cm,
Perimeter = 4 × 7 = 28 cm
✨ Why do we use Letter-Numbers?
✔ Saves time
✔ Avoids long sentences
✔ Works for all values
✔ Makes patterns easy to understand
This is why algebra is very powerful.
📌 Key Points to Remember
Letters can represent numbers
Expressions like a + 3, 2n, 35c + 60j are called algebraic expressions
Replace the letter with a number to get the answer
👉 Next Post (Part 2) will cover:
Removing the multiplication sign (like 2n)
Simplifying expressions
Like and unlike terms
Fun patterns with calendars and matchsticks