Class 8 Maths - ODISHA
Number Play
The chapter 'Number Play' in Class 8 Mathematics for Odisha (BSE) introduces students to the fascinating world of numbers through puzzles, riddles, and mathematical tricks. It focuses on expressing 2-digit and 3-digit numbers in their generalized forms using algebra (like 10a + b). This chapter helps students understand our base-10 number system deeply and strengthens logical thinking, divisibility rules for 2, 3, 5, 9, and 10, and algebraic reasoning. It is crucial for board exam preparation as it bridges basic arithmetic with foundational algebra, often appearing in 2-to-4 mark short-answer and puzzle-solving questions.
Start Learning FreeKey Concepts
Generalized Form of a 2-Digit Number
Any 2-digit number formed by digits 'a' (tens digit) and 'b' (units digit) can be written algebraically as 10a + b.
Generalized Form of a 3-Digit Number
A 3-digit number with hundreds digit 'a', tens digit 'b', and units digit 'c' is represented as 100a + 10b + c.
Reversing Digits of a Number
When the digits of a 2-digit number (10a + b) are reversed, the new number becomes 10b + a.
Divisibility by 9 and 3
A number is divisible by 9 or 3 if the sum of its digits is a multiple of 9 or 3, respectively.
Divisibility by 10, 5, and 2
A number is divisible by 10 if its unit digit is 0, by 5 if the unit digit is 0 or 5, and by 2 if the unit digit is even.
Important Formulas
Board Exam Info
In the Odisha (BSE) Class 8 Mathematics examinations, 'Number Play' typically carries around 3 to 5 marks. Common question types include finding unknown digits in addition or multiplication puzzles, proving divisibility rules using generalized forms, and solving word problems based on reversing the digits of a 2-digit number.
Frequently Asked Questions
Why do we write numbers like 10a + b instead of just ab?
In algebra, writing 'ab' means 'a multiplied by b'. To represent a 2-digit number where 'a' is the tens digit and 'b' is the units digit, we must use the expanded form 10a + b.
How do I solve puzzle questions where letters represent digits?
Look at the unit column first to find clues about possible digit values through trial and method, keeping in mind that each letter represents a single digit from 0 to 9.
Are the divisibility tricks necessary for BSE board exams?
Yes, questions often ask you to explain why a certain number is divisible by 3 or 9 using its generalized algebraic form rather than just performing long division.
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