Class 8 Maths - HARYANA
Number Play
The chapter 'Number Play' in Class 8 Mathematics helps students explore the fascinating world of numbers through puzzles, riddles, and general properties. Designed according to the Haryana Board (BSEH) syllabus, it teaches students how numbers can be represented in generalized forms using algebraic variables like 'a', 'b', and 'c'. By understanding the place value system, children learn tricks to quickly check divisibility by numbers such as 2, 3, 5, 9, and 10 without doing actual division. This chapter builds a strong foundation for logical thinking, number sense, and algebra, making it scoring and important for school exams.
Start Learning FreeKey Concepts
Generalized Form of Numbers
Writing a two-digit number like 'ab' as (10a + b) and a three-digit number like 'abc' as (100a + 10b + c) using their place values.
Divisibility by 2, 5, and 10
A number is divisible by 2 if its unit digit is even, by 5 if the last digit is 0 or 5, and by 10 if the last digit is 0.
Divisibility by 3 and 9
A number is divisible by 3 or 9 if the sum of all its digits is a multiple of 3 or 9 respectively.
Number Puzzles and Cryptarithms
Solving mathematical puzzles where letters or symbols take the place of digits in arithmetic operations like addition or multiplication.
Reversing Digits
Understanding how the sum or difference of a two-digit number and the number formed by reversing its digits behaves mathematically.
Important Formulas
Board Exam Info
In the Haryana Board (BSEH) Class 8 Mathematics exams, 'Number Play' typically carries around 4 to 6 marks. Common question types include short-answer questions on checking divisibility rules, medium-length puzzle problems involving letter substitution (cryptarithms), and word problems based on the generalized form of two-digit numbers.
Frequently Asked Questions
Why do we write numbers like 10a + b instead of just ab?
Writing it as 10a + b separates the tens digit (a) from the units digit (b), which is necessary to apply algebraic methods and solve number puzzles.
How can I easily solve letter-replacement puzzles (cryptarithms)?
Start by looking at the units column to find clues, check for carries, and use trial and error with single digits (0 to 9) that fit the addition or multiplication rules.
Are divisibility rules applicable to negative numbers?
Divisibility rules in this chapter are primarily taught for positive whole numbers based on their place value representations.
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