The chapter covers divisibility by 10, divisibility by 2, divisibility by 3, divisibility by 5, divisibility by 9, games with numbers, letters for digits, numbers in a general form. The Maths chapter 5 Playing with numbers deals with all the important fundamentals necessary to develop an understanding. The chapter has theoretical explanations for all concepts, along with simple and detailed examples.
In this chapter, forming the numbers, reversing the numbers, and expressing numbers in words are explained. In reversing the numbers, we can reverse a two-digit number and perform applications in a set of algorithms. The numbers can be defined by denoting certain digits and hence finding missing numbers by using the conditions given. The chapter teaches interesting concepts like interchanging the digits of numbers with lots of examples and exercises. The generalised form of numbers is explained. A number is indeed generalised if it can be represented as the product of its digits and their associated place values. Divisibility rules are a collection of generic principles used to assess if an integer is evenly divisible by another number. Some of the examples for divisibility rules are
Problems based on addition and multiplication of cryptarithms (cryptarithms are puzzles that operate on various mathematical operations and numbers, such as in which letters take digits and one must figure out which letter represents which digit) are discussed in the final unit of this chapter. Applications of cryptarithms are also highly essential in higher grades. Furthermore, the topic forms the basis of coding, cryptography, cybersecurity and thus, learning the notion of this topic is critical.