NCERT Class 7 Maths Chapter 6
Number Play
This chapter from Ganita Prakash Part 1 engages CBSE Class 7 students with interesting patterns, puzzles, and properties of numbers, including divisibility rules, factors, multiples, and prime numbers. Students explore number games, magic squares, palindromes, and patterns in number sequences. The chapter fosters mathematical curiosity and logical thinking through playful exploration of numerical properties.
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Key Terms
- Divisibility Rule
- A shortcut to determine if a number is divisible by another number without performing the full division. For example, a number is divisible by 3 if the sum of its digits is divisible by 3.
- Prime Number
- A natural number greater than 1 that has exactly two factors: 1 and itself. Examples include 2, 3, 5, 7, 11, and 13.
- Composite Number
- A natural number greater than 1 that has more than two factors, meaning it can be divided evenly by numbers other than 1 and itself. Examples include 4, 6, 9, and 15.
- Factor
- A number that divides another number exactly without leaving a remainder. For example, the factors of 12 are 1, 2, 3, 4, 6, and 12.
- Multiple
- A number obtained by multiplying a given number by any positive integer. For example, the multiples of 4 are 4, 8, 12, 16, 20, and so on.
- Palindrome Number
- A number that reads the same forwards and backwards, such as 121, 1331, and 12321. Palindromic numbers often arise through interesting number patterns.
Frequently Asked Questions
What are the divisibility rules for 2, 3, 5, and 9?▾
A number is divisible by 2 if its last digit is even. It is divisible by 3 if the sum of its digits is divisible by 3. It is divisible by 5 if the last digit is 0 or 5. It is divisible by 9 if the sum of its digits is divisible by 9.
What is the difference between prime and composite numbers?▾
A prime number has exactly two factors — 1 and itself (e.g., 7). A composite number has more than two factors (e.g., 12 has factors 1, 2, 3, 4, 6, 12). The number 1 is neither prime nor composite.
What is a magic square in Class 7 Maths?▾
A magic square is a grid of numbers arranged so that the sum of every row, column, and diagonal is the same. This constant sum is called the magic constant. Creating and solving magic squares is an interesting number puzzle covered in this chapter.
What are factors and multiples? Give examples.▾
Factors are numbers that divide a given number exactly. For example, factors of 18 are 1, 2, 3, 6, 9, and 18. Multiples are numbers obtained by multiplying a number by natural numbers. For example, multiples of 5 are 5, 10, 15, 20, etc.
What is a palindrome number and how is it formed?▾
A palindrome number reads the same forwards and backwards, like 121 or 1331. An interesting method: take any number, reverse it, and add them together. Repeat until you get a palindrome. For example: 56 + 65 = 121, which is a palindrome in just one step.
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