Algebra Chapter Notes | Mental Maths - Class 1 PDF Download

What is Algebra?

Algebra is a part of Mathematics where we use numbers, symbols, and letters to find answers. It helps us solve problems and find missing numbers.

Imagine you have a box with some candies inside, but you don’t know how many. If someone tells you, "There are 5 more candies in another box, and together they make 10," you can figure out how many candies were in the first box. This is what Algebra helps us do—find missing numbers.

Example:

• 2 + _______ = 5 → What number should go in the blank?
• The missing number that should go in blank is 3 because 2 + 3 = 5.

Algebra makes problem-solving fun and easy by helping us find unknown values in different situations.

What are Patterns?

A pattern is something that repeats again and again in the same way. It could be numbers, shapes, or objects arranged in a particular order. When we understand patterns, we can predict what comes next.

Patterns are everywhere! You can find them in clothes, floor tiles, and even in music. Learning patterns in numbers and shapes makes math easier and more interesting.

Types of Patterns:

1. Number Patterns

Number patterns follow a rule where numbers increase or decrease in a set way. These patterns help us in counting and calculations.

Example:

2, 4, 6, 8, __, __ → What comes next?

• The pattern adds 2 each time.
• The missing numbers are 10 and 12.

10, 9, 8, 7, __, __ → What comes next?

• The pattern subtracts 1 each time.
• The missing numbers are 6 and 5.

2. Shape Patterns

Shapes can also be arranged in a pattern. A shape pattern repeats in a certain way.

(What comes next?)
The pattern repeats after every 2 blue circles, then 1 red.
So, the next shape is Blue Circle.
Learning patterns makes it easier to understand numbers and shapes in daily life.

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What are Variables?

A variable is a missing number or a letter that can take different values. Instead of using a blank space, we use letters like x or y to represent unknown numbers.

Think of a mystery box with a surprise inside. Until you open it, you don’t know what’s inside! A variable is like that mystery box in math.

Example:

x + 3 = 7

• Here, x is a variable.
• To find x, we think: "What number plus 3 gives 7?"
• x = 4 because 4 + 3 = 7.

5 - y = 2

• Here, y = 3 because 5 - 3 = 2.

Finding the Missing Number in Addition

Sometimes, we need to find a missing number in a sum. This is an important part of Algebra.

Example:

4 + __ = 9

• What number do we add to 4 to make 9?
• The answer is 5.
• 4 + 5 = 9.

__ + 6 = 10

• The missing number is 4 because 4 + 6 = 10.

Finding missing numbers helps us understand how addition works in real life.

Finding the Missing Number in Subtraction

We can also find missing numbers in subtraction. This helps us solve problems easily.

Example:

10 - __ = 6

• What number do we subtract from 10 to get 6?
• The missing number is 4.
• 10 - 4 = 6.

__ - 3 = 2

• The missing number is 5 because 5 - 3 = 2.

By practicing missing numbers in subtraction, we improve our problem-solving skills.

Writing Simple Equations

An equation is a math sentence with an = (equal sign). It shows that both sides are balanced.

Example:

• 3 + 2 = 5 (Addition equation)
• 7 - 4 = 3 (Subtraction equation)

x + 5 = 10 (We need to find x)

• x = 5 because 5 + 5 = 10.

Using equations helps us solve real-life problems quickly.

Understanding Greater Than, Less Than, and Equal To

We compare numbers using these signs:

• > (Greater than) → Shows that a number is bigger.
• < (Less than) → Shows that a number is smaller.
• = (Equal to) → Shows that two numbers are the same.

Example:

• 5 > 3 (5 is greater than 3)
• 2 < 4 (2 is less than 4)
• 6 = 6 (Both numbers are equal)

Understanding these signs helps us compare numbers easily.

Simple Word Problems Using Algebra

Word problems help us use algebra in real life.

Example 1:

• Rohan has 3 apples. His mother gives him some more apples. Now he has 8 apples.
• How many apples did his mother give him?
• 3 + x = 8
• x = 5 → His mother gave him 5 apples.

Example 2:

• A basket had 10 oranges. Sita took some oranges and now there are 6 left.
• How many did Sita take?
• 10 - y = 6
• y = 4 → Sita took 4 oranges.

Word problems make algebra fun and useful in daily life.

Summary

• Algebra helps us find missing numbers using patterns and equations.
• A variable (like x or y) is a number we don’t know yet.
• We use addition and subtraction to find missing numbers.
• Patterns help us predict what comes next.
• Word problems show how algebra is used in daily life.