If the length of a rectangle is l and its breadth is 3, what is the expression for its perimeter?
Answer and explanation
Correct answer: 2(l + 3)
The perimeter of a rectangle is the total length around its boundary. A rectangle has two equal lengths and two equal breadths, so its perimeter is found by adding l+3+l+3. This can also be written as twice the sum of one length and one breadth: P=2(l+3). The symbol l is an algebraic variable, so it should remain in the expression.
Substituting the given dimensions directly gives P=2(l+3)=2l+6. Option A gives only one length plus one breadth and is therefore half the perimeter. Option B is an area-like product and does not represent a boundary length, while option C has an unsuitable squared term. Hence option D, 2(l+3), is the correct expression.
Frequently asked questions
What is the correct answer to this question?
2(l + 3)
Why is this the correct answer?
The perimeter of a rectangle is the total length around its boundary. A rectangle has two equal lengths and two equal breadths, so its perimeter is found by adding l+3+l+3. This can also be written as twice the sum of one length and one breadth: P=2(l+3). The symbol l is an algebraic variable, so it should remain in the expression.
Substituting the given dimensions directly gives P=2(l+3)=2l+6. Option A gives only one length plus one breadth and is therefore half the perimeter. Option B is an area-like product and does not represent a boundary length, while option C has an unsuitable squared term. Hence option D, 2(l+3), is the correct expression.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Introduction to Polynomials. Topic: Algebraic expressions.
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