NCERT Class 7 Maths Chapter 4
Expressions Using Letter-Numbers
This chapter from Ganita Prakash Part 1 introduces CBSE Class 7 students to the fundamentals of algebra by using letters to represent unknown numbers. Students learn to form algebraic expressions, identify variables and constants, evaluate expressions for given values, and translate verbal statements into algebraic form. This chapter builds the essential language of algebra used in higher mathematics.
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Key Terms
- Variable
- A letter (like x, y, or n) used to represent an unknown or changing quantity in an algebraic expression or equation.
- Constant
- A fixed numerical value that does not change in an expression or equation. For example, in the expression 3x + 5, the number 5 is a constant.
- Algebraic Expression
- A combination of variables, constants, and mathematical operations. For example, 4x + 7 is an algebraic expression where x is a variable.
- Coefficient
- The numerical factor multiplied by a variable in a term. For example, in 5y, the coefficient of y is 5.
- Term
- A single part of an algebraic expression, which can be a number, a variable, or a product of numbers and variables. In 3x + 4y – 2, the terms are 3x, 4y, and –2.
- Evaluating an Expression
- The process of finding the numerical value of an algebraic expression by substituting a given value for each variable.
Frequently Asked Questions
What is a variable in algebra for Class 7?▾
A variable is a letter, such as x, y, or n, used to represent an unknown or changing quantity. For example, if a bag has x marbles, x is a variable that can take different values depending on how many marbles are in the bag.
What is the difference between a variable and a constant?▾
A variable is a letter whose value can change or is unknown, like x or y. A constant is a fixed number that does not change, like 5 or 100. In the expression 2x + 7, x is the variable and 7 is the constant.
How do you evaluate an algebraic expression?▾
To evaluate an expression, substitute the given numerical value in place of the variable and perform the operations. For example, to evaluate 3x + 5 when x = 4: substitute to get 3(4) + 5 = 12 + 5 = 17.
How do you write a word problem as an algebraic expression?▾
Identify the unknown quantity and assign it a variable. Then use the mathematical operations described in the problem. For example, 'five more than a number n' becomes n + 5, and 'three times a number decreased by 4' becomes 3n – 4.
What is the coefficient of a variable?▾
The coefficient is the number multiplied by the variable in a term. In 7x, the coefficient is 7. In –3y, the coefficient is –3. If a variable is written alone like x, its coefficient is understood to be 1.
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