Class 7 Maths - HARYANA
Number Play
The chapter 'Number Play' in Class 7 Mathematics for Haryana (BSEH) introduces students to fascinating patterns and puzzles involving numbers. It builds strong logical thinking and computational skills by exploring properties of numbers, divisibility rules, and algebraic representations of two-digit and three-digit numbers. Understanding this chapter is essential not only for scoring well in BSEH board exams but also for developing a solid foundation in number theory, which helps in solving complex arithmetic and algebra problems quickly and accurately during competitive examinations.
Start Learning FreeKey Concepts
General Form of Numbers
Any two-digit number like ab can be written in expanded algebraic form as 10a + b, where 'a' is the tens digit and 'b' is the units digit.
Reversing Digits
When the digits of a two-digit number ab are reversed, the new number becomes ba, which is expressed as 10b + a in algebraic form.
Divisibility by 9 and 11
A number is divisible by 9 if the sum of its digits is a multiple of 9. A number is divisible by 11 if the difference between the sum of its odd-place digits and even-place digits is 0 or a multiple of 11.
Number Puzzles and Cryptarithms
Puzzles where letters or symbols take the place of digits in arithmetic operations, solved using logic and basic properties of number addition and multiplication.
Properties of Factors and Multiples
Exploring interesting patterns when adding or subtracting numbers and their reversals, such as the sum of a number and its reverse always being divisible by 11.
Important Formulas
Board Exam Info
In the Haryana (BSEH) Class 7 Mathematics exams, this chapter typically carries around 4 to 6 marks. Common question types include writing numbers in general expanded form, proving divisibility rules using algebra, solving letter puzzles (cryptarithms) where letters represent unknown digits, and finding sums or differences of reversed numbers.
Frequently Asked Questions
What does writing a number in 'general form' mean?
It means writing a number according to its place value in algebraic form. For example, the number 45 is written as 10(4) + 5.
Why is the sum of a two-digit number and its reverse always divisible by 11?
Because the sum evaluates to 11(a + b), which contains 11 as a factor, meaning it can always be divided evenly by 11.
How do we solve letter puzzles in Number Play?
We use logic and trial-and-error based on basic addition and multiplication facts, keeping in mind that each letter represents a single digit from 0 to 9.
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