NCERT Class7 Maths Formation of Algebric expression

Forming Algebraic Expressions

Instructions

Let the unknown number be represented by x (and y where required).
Read each statement carefully and write the correct algebraic expression.
Each question includes its expression and a short explanation for better understanding.

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Section A: Basic Questions

1. Statement: Ramesh has some pencils and buys 6 more.
Expression: x + 6
Explanation: Buying more means adding 6 to the number.

2. Statement: A number is multiplied by 9.
Expression: 9x
Explanation: Multiplying by 9 gives .

3. Statement: A number is decreased by 11.
Expression: x - 11
Explanation: “Decreased” means subtract.

4. Statement: The length of a rectangle is 5 cm more than its breadth .
Expression: length = breadth + 5
Explanation: “More than” means addition.

5. Statement: The cost of one notebook is 40 ₹. Find the cost of 8 notebooks.
Expression: 40 x 8 = 320 ₹
Explanation: Cost is multiplied by 8.

6. Statement: Half of a number is increased by 7.
Expression: x/2 + 7
Explanation: Take half first, then add 7.

7. Statement: Rahul’s age is x  years. His sister is 4 years younger.
Expression: Age of Rahul's sister = x - 4
Explanation: “Younger” means subtracting years.

8. Statement: A number is tripled and then 2 is added.
Expression: 3x + 2
Explanation: Multiply first, then add.

9. Statement: Write the perimeter of a square of side 8 cm.
Expression: P= 4 x 8 = 32 cm
Explanation: Perimeter of a square = . 32 cm

10. Statement: Write the sum of a number and its double.
Expression: x + 2x = 3x
Explanation: Double of is .

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Section B: Higher-Level Questions

11. Statement: The sum of a number and 5 is multiplied by 3.
Expression: 3( x + 5 )= 3x+15
Explanation: Add inside brackets, then multiply.

12. Statement: A number is divided by 4 and then decreased by 6.
Expression: x/4 - 6
Explanation: Perform division before subtraction.

13. Statement: Five less than twice a number.
Expression: 2x - 5
Explanation: “Less than” indicates subtraction.

14. Statement: The product of a number and the sum of 3 and 7.
Expression: a x (3+7) = 10a
Explanation: Add first, then multiply by .

15. Statement: Find the perimeter of a rectangle whose length is 10 cm and 8 breadth is cm.
Expression: p = 2(l+b) = 2(10+8) = 36 cm
Explanation: Perimeter of a rectangle = .

16. Statement: Three times a number reduced by half of the same number.
Expression: 3x -x/2
Explanation: Subtract half from three times the number.

17. Statement: Write the sum of two consecutive numbers.
Expression: 3+4= 7
Explanation: Consecutive numbers differ by 1.

18. Statement: Find the area of a square whose side is 6  cm.
Expression: a= side x side = 6x6 = 36 sq cm
Explanation: Area of a square = side².

19. Statement: Find the total cost of 6  pens at ₹5 each and 3 notebooks at 30 ₹ each.
Expression:  6x5 + 30x3 = 30+90 = 120 ₹
Explanation: Add the costs of both items.

20. Statement: One-fourth of a number is added to three times the same number.
Expression:x/4 + 3x
Explanation: Add fractional and multiple terms.