5.4 - Finding the Square of a Number

Interactive Audio Lesson

Listen to a student-teacher conversation explaining the topic in a relatable way.

Finding the Square of Large Numbers

Unlock Audio Lesson

Signup and Enroll to the course for listening the Audio Lesson

Teacher
Teacher

Today, we're going to learn about finding the square of larger numbers without direct multiplication. For example, how would we find the square of 23?

Student 1
Student 1

Wouldn’t we just do 23 times 23?

Teacher
Teacher

Yes, but that’s tedious for larger numbers! Instead, we can express 23 as 20 plus 3, then use the identity (a + b)². Can anyone repeat the formula?

Student 2
Student 2

(a + b)² = a² + 2ab + b²!

Teacher
Teacher

Great job! Now applying this to 23: (20 + 3)² becomes 20² + 2 * 20 * 3 + 3². What do we get?

Student 3
Student 3

That’s 400 + 120 + 9, which equals 529!

Teacher
Teacher

Exactly! Remember the key: breaking the number into parts can simplify calculations.

Squares of Numbers Ending in 5

Unlock Audio Lesson

Signup and Enroll to the course for listening the Audio Lesson

Teacher
Teacher

Now let’s talk about a special case. How do we find the square of numbers ending in 5, like 35?

Student 2
Student 2

Do we still use the formula?

Teacher
Teacher

Absolutely! But first, observe the pattern: (a5)² = [a(a + 1) * 100] + 25. Can anyone explain this?

Student 4
Student 4

It seems like we multiply the a part by its next integer, then use that in hundreds and add 25.

Teacher
Teacher

Exactly! So for 35, what do we have?

Student 1
Student 1

3 * 4 equals 12, so it’s 1225!

Teacher
Teacher

Perfect! Make sure to remember this shortcut for squaring numbers ending in 5.

Introduction to Pythagorean Triplets

Unlock Audio Lesson

Signup and Enroll to the course for listening the Audio Lesson

Teacher
Teacher

Next, we will explore Pythagorean triplets. What do you know about them?

Student 3
Student 3

Aren’t they sets of three numbers where the square of one equals the sum of the squares of the other two?

Teacher
Teacher

Exactly! For example, 3, 4, and 5 is a triplet because 3² + 4² = 5². Can someone provide another example?

Student 4
Student 4

I think 6, 8, 10 is also one!

Teacher
Teacher

Right again! Does anyone know how we can generate more Pythagorean triplets?

Student 1
Student 1

I recall something about using a formula involving natural numbers?

Teacher
Teacher

Yes! For any natural number m > 1, (2m)² + (m² - 1)² = (m² + 1)². Let’s try to find one with the smallest member being 6.

Student 2
Student 2

We would set 2m = 6, so m is 3, leading to 6, 8, and 10 then!

Teacher
Teacher

Fantastic! Keep practicing generating those!

Introduction & Overview

Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.

Quick Overview

This section discusses methods to calculate the square of a number efficiently, particularly without direct multiplication.

Standard

The section illustrates techniques to find the square of larger numbers by using the identity
(a + b)² = a² + 2ab + b². It also explores special cases of squaring numbers ending in 5 and introduces the concept of Pythagorean triplets.

Detailed

Finding the Square of a Number

In this section, we explore how to find the square of larger numbers without multiplying them directly. The fundamental identity used is:

(a + b)² = a² + 2ab + b²

For instance, for the number 23, we can break it down into (20 + 3). Hence, the square is calculated as:

(20 + 3)² = 20² + 2 * 20 * 3 + 3² = 400 + 120 + 9 = 529.

We also consider special patterns for numbers ending in 5, such as (a5)² = [a(a + 1) * 100] + 25, and illustrate this with examples.

Lastly, the section briefly discusses Pythagorean triplets and introduces a formula for generating them using natural numbers, showcasing the relationship of squares between certain integer sets.

Youtube Videos

Finding the Square of a Number - Squares and Square Roots | Class 8 Maths Chapter 5 | CBSE 2024-25
Finding the Square of a Number - Squares and Square Roots | Class 8 Maths Chapter 5 | CBSE 2024-25
Cube Root Math Trick
Cube Root Math Trick
Class 8 CBSE Maths | Squares and Square Roots - Finding Square Root by Division | Xylem Class 8 CBSE
Class 8 CBSE Maths | Squares and Square Roots - Finding Square Root by Division | Xylem Class 8 CBSE
Square and Square Roots in One Shot | Maths - Class 8th | Umang | Physics Wallah
Square and Square Roots in One Shot | Maths - Class 8th | Umang | Physics Wallah
Squares and Square Roots || 8 Min || CBSE Class 8 Math Rapid Revision || Ayush Sir
Squares and Square Roots || 8 Min || CBSE Class 8 Math Rapid Revision || Ayush Sir
Class 8 Maths Chapter 5 Try These Questions Page no 52 & 53 | Squares and Square Roots | CBSE 8th
Class 8 Maths Chapter 5 Try These Questions Page no 52 & 53 | Squares and Square Roots | CBSE 8th
Q 9 - Ex 5.1 - Square and Square Roots - NCERT Maths Class 8th - Chapter 5, New Syllabus CBSE 2023
Q 9 - Ex 5.1 - Square and Square Roots - NCERT Maths Class 8th - Chapter 5, New Syllabus CBSE 2023
Short Tricks on Square Root in 5 Seconds #shorttricks #shorttricksmaths #shorts
Short Tricks on Square Root in 5 Seconds #shorttricks #shorttricksmaths #shorts
Square roots of Decimals : Division Method | Class 8 | CBSE | NCERT | ICSE
Square roots of Decimals : Division Method | Class 8 | CBSE | NCERT | ICSE
Class 8 CBSE Maths | Squares & Square Roots - One Shot | Xylem Class 8 CBSE
Class 8 CBSE Maths | Squares & Square Roots - One Shot | Xylem Class 8 CBSE

Audio Book

Dive deep into the subject with an immersive audiobook experience.

Finding Squares Easily

Unlock Audio Book

Signup and Enroll to the course for listening the Audio Book

Squares of small numbers like 3, 4, 5, 6, 7, ... etc. are easy to find. But can we find the square of 23 so quickly? The answer is not so easy and we may need to multiply 23 by 23.

Detailed Explanation

Calculating the square of smaller numbers, such as 3, 4, 5, or 6, can be done easily because we memorize their squares. However, for larger numbers like 23, it can be tedious to rely on simple multiplication. This shows that although squaring is easy for small numbers, it becomes cumbersome for larger numbers.

Examples & Analogies

Imagine if you regularly bake cookies. You have memorized the recipe for a dozen cookies (small number), but if someone asks you to bake 23 dozen, you might need to consult your notes or a calculator for accurate measurements.

Using the Formula

Unlock Audio Book

Signup and Enroll to the course for listening the Audio Book

There is a way to find this without having to multiply 23 × 23. We know 23 = 20 + 3.
Therefore 23² = (20 + 3)² = 20(20 + 3) + 3(20 + 3) = 20² + 20 × 3 + 3 × 20 + 3² = 400 + 60 + 60 + 9 = 529.

Detailed Explanation

To calculate the square of 23, we break it down into a sum, (20 + 3). This utilizes the algebraic identity for squaring a number: (a + b)² = a² + 2ab + b². By simplifying this, we arrive at the answer without direct multiplication, showing a pattern and structure in numbers that helps facilitate calculations.

Examples & Analogies

Think of a recipe where you have to double ingredients. Instead of measuring out each ingredient twice, you can simply calculate 2 times the amount of a single serving, making it both easy and more efficient.

Examples in Action

Unlock Audio Book

Signup and Enroll to the course for listening the Audio Book

Example 1: Find the square of the following numbers without actual multiplication. (i) 39 (ii) 42.
Solution: (i) 39² = (30 + 9)² = 30(30 + 9) + 9(30 + 9) = 30² + 30 × 9 + 9 × 30 + 9² = 900 + 270 + 270 + 81 = 1521.
(ii) 42² = (40 + 2)² = 40(40 + 2) + 2(40 + 2) = 40² + 40 × 2 + 2 × 40 + 2² = 1600 + 80 + 80 + 4 = 1764.

Detailed Explanation

In this section, we calculate the squares of two numbers, 39 and 42, using the addition method we learned earlier. For 39, we broke it down as (30 + 9) and for 42, we used (40 + 2). This method allows us to avoid direct multiplication by using previously solved squares and the distributive property of multiplication.

Examples & Analogies

Imagine organizing your wardrobe. Instead of buying clothes in bulk and estimating sizes, you can take careful measurements and find that a specific combination gives you the fit you need, just like combining smaller number segments makes squaring easier and more accurate.

Patterns in Squaring Numbers

Unlock Audio Book

Signup and Enroll to the course for listening the Audio Book

5.4.1 Other patterns in squares. Consider the following pattern: 25² = 625 = (2 × 3) hundreds + 25.

Detailed Explanation

This chunk discusses recognizing patterns in numbers, particularly when the unit digit is 5. It shows that the square of any number ending in 5 can be found using a specific pattern: (a × (a + 1)) hundreds + 25, which greatly simplifies calculations.

Examples & Analogies

Think of how certain flower arrangements can follow specific patterns based on the number of stems. Recognizing this pattern helps you create beautiful bouquets efficiently without having to calculate each combination from scratch.

Introduction to Pythagorean Triplets

Unlock Audio Book

Signup and Enroll to the course for listening the Audio Book

5.4.2 Pythagorean triplets. Consider the following (3² + 4² = 5²). The collection of numbers 3, 4, and 5 is known as a Pythagorean triplet.

Detailed Explanation

A Pythagorean triplet consists of three positive integers a, b, and c, such that a² + b² = c². This chunk presents basic examples like (3, 4, 5) and illustrates their relevance in finding relationships between squares of numbers. This concept is especially significant in geometry, as it helps in calculations regarding right triangles.

Examples & Analogies

Consider a ladder leaning against a wall. The length of the ladder, the distance from the wall, and the height up the wall forms a right triangle, similar to how the Pythagorean triplet provides a method to determine these distances.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • Algebraic Identity: Understanding the identity used for finding squares.

  • Squares of Numbers Ending in 5: A specific case that simplifies calculation.

  • Pythagorean Triplets: Sets of three numbers that satisfy the Pythagorean theorem.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • To find the square of 39 without actual multiplication: (30 + 9)² = 30² + 2(30)(9) + 9² = 900 + 540 + 81 = 1521.

  • Finding the square of 95: (90 + 5)² = 90² + 2(90)(5) + 5² = 8100 + 900 + 25 = 9025.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎵 Rhymes Time

  • To find the square choose a and b; add their square for what you see!

📖 Fascinating Stories

  • A student wanted to simplify, found the square of 23 with a clever trick, turning it into a party of tens and ones that made it lick!

🧠 Other Memory Gems

  • Pythagorean triplet: '2M' for 2m, then m²-1, m²+1 for fun!

🎯 Super Acronyms

SQUARE

  • Split
  • Use
  • Apply
  • Result
  • Add
  • Evaluate!

Flash Cards

Review key concepts with flashcards.

Glossary of Terms

Review the Definitions for terms.

  • Term: Square of a Number

    Definition:

    The result of multiplying a number by itself.

  • Term: Pythagorean Triplet

    Definition:

    A set of three positive integers a, b, and c, such that a² + b² = c².

  • Term: Algebraic Identity

    Definition:

    An equality that holds for any values of its variables.