Introduction to Linear Polynomials | Exercise 2.3

Question 3

Suppose the length of a rectangle is 13 cm. Find the area if the breadth is (i) 12 cm, (ii) 10 cm, (iii) 8 cm. Find the linear pattern representing the area of the rectangle.

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Solution

Let's find the area of the rectangle using the given length and different breadths.

Step 1 — Calculate Area for Breadth = 12 cm

We know the length is 13 cm.

The breadth is 12 cm.

The area of a rectangle is length multiplied by breadth.

Area=Length×Breadth\text{Area} = \text{Length} \times \text{Breadth}

=13×12= 13 \times 12

156 cm2\boxed{156 \text{ cm}^2}

Step 2 — Calculate Area for Breadth = 10 cm

The length remains 13 cm.

The breadth is now 10 cm.

Let's use the area formula again.

Area=Length×Breadth\text{Area} = \text{Length} \times \text{Breadth}

=13×10= 13 \times 10

130 cm2\boxed{130 \text{ cm}^2}

Step 3 — Calculate Area for Breadth = 8 cm

The length is still 13 cm.

The breadth is 8 cm.

We will apply the area formula one more time.

Area=Length×Breadth\text{Area} = \text{Length} \times \text{Breadth}

=13×8= 13 \times 8

104 cm2\boxed{104 \text{ cm}^2}

Step 4 — Find the Linear Pattern

Let's represent the breadth as a variable.

Let the breadth be xx cm.

The length of the rectangle is fixed at 13 cm.

The area (A) is length multiplied by breadth.

A=13×xA = 13 \times x

A=13x\boxed{A = 13x}

Diagram 1

Answer

(i) The area is 156 cm2156 \text{ cm}^2. (ii) The area is 130 cm2130 \text{ cm}^2. (iii) The area is 104 cm2104 \text{ cm}^2. The linear pattern representing the area is A=13xA = 13x.

More questions in Exercise 2.3

Q1

Solve the following:

  1. A student has ₹500 in her savings bank account. She gets ₹150 every month as pocket money. How much money will she have at the end of every month from the second month onwards? Find a linear expression to represent the amount she will have in the nthn^{\text{th}} month.
Q2

A rally starts with 120 members. Each hour, 9 members drop out of the group. How many members will remain after 1, 2, 3, ... hours? Find a linear expression to represent the number of members at the end of the nthn^{\text{th}} hour.

Q3

Suppose the length of a rectangle is 13 cm. Find the area if the breadth is (i) 12 cm, (ii) 10 cm, (iii) 8 cm. Find the linear pattern representing the area of the rectangle.

Q4

Suppose the length of a rectangular box is 7 cm and breadth is 11 cm. Find the volume if the height is (i) 5 cm, (ii) 9 cm, (iii) 13 cm. Find the linear pattern representing the volume of the rectangular box.

Q5

Sarita is reading a book of 500 pages. She reads 20 pages every day. How many pages will be left after 15 days? Express this as a linear pattern.

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