Master Chapter 5 Class 6 - Prime Time (Ganita Prakash) with comprehensive NCERT Solutions, Practice Questions, MCQs, Sample Papers, Case Based Questions, and Video lessons.
Start Learning NowWelcome to Chapter 5, Prime Time, from your Class 6 Maths book, Ganita Prakash.
This chapter is one of the most important and fascinating in all of mathematics. It’s all about discovering the secret ingredients, the fundamental "building blocks," that all whole numbers are made of.
We often think of numbers as a simple, endless line. But this chapter asks you to think of them differently—like structures. Some numbers, like 12, are like a house built from smaller bricks. You can arrange 12 figs in 2 × 6 rows or 3 × 4 rows. Other numbers, like 7, are like a solid, uncut diamond. You can only arrange 7 figs in a single 1 × 7 row.
This core difference is what we will explore. We will learn the language and tools to take any number, no matter how large, and break it down into its smallest, indivisible parts. This chapter is a journey from playing simple number games to understanding a deep and powerful mathematical tool.
This chapter is a logical progression. We will start with the basic relationships between numbers and build up to a "master tool" for understanding them.
Common Multiples and Factors: We begin by playing two games.
The "Idli-Vada" game introduces you to Multiples, which are the results of skip-counting (e.g., multiples of 3 are 3, 6, 9...). When two players have to say "Idli-Vada" at the same time (e.g., for a multiple of both 3 and 5), we discover the idea of Common Multiples.
The "Jump Jackpot" game introduces Factors, which are the numbers that divide another number exactly (e.g., factors of 24 are 1, 2, 3, 4, 6, 8, 12, 24). When a player must find one jump size to land on two different treasures, we discover Common Factors.
Prime and Composite Numbers: This is the heart of the chapter. You will learn the formal definitions for the "uncut diamonds" and the "houses."
Prime Numbers: Numbers (like 2, 3, 5, 7, 11...) that have only two factors: 1 and themselves.
Composite Numbers: Numbers (like 4, 6, 8, 9, 12...) that have more than two factors.
You will also learn about the number 1, which is special and is considered neither prime nor composite.
We will use a famous and ancient method called the Sieve of Eratosthenes to systematically find all the prime numbers up to 100.
Co-prime Numbers: We will learn about a special relationship between two numbers. Two numbers are co-prime if they have no common factors other than 1 (for example, 4 and 9).
Prime Factorisation: This is the "master tool." You will learn how to take any composite number and break it down into a product of only prime numbers (e.g., 36 = 2 × 2 × 3 × 3). We will see that this combination of primes is unique for every number. This powerful technique will then allow us to systematically check for divisibility and find common factors for very large numbers.
Divisibility Tests: Finally, you will learn the "shortcuts." Instead of doing long division, you will learn the simple rules to quickly check if a large number is divisible by 2, 4, 5, 8, and 10 just by looking at its last few digits.
This chapter builds concept upon concept. It can feel like a big jump to go from playing games to using prime factorization. The best way to learn this is to see the connection between the game and the method, step-by-step. At Teachoo, we don't just give you the answer; we walk you through the entire process, from the initial puzzle to the final, formal solution. We help you build the foundation so you can use these tools with confidence.
To begin your journey into the world of primes, please click on any topic link to get started.