Introduction to Linear Polynomials | Exercise 2.3

Question 1

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.
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Solution

We need to find the total money after each month. We will then write a general expression.

Step 1 — Calculate monthly amounts

The student starts with ₹500. She gets ₹150 every month. Let's calculate the money at the end of each month.

At the end of the 2nd month: =500+(2×150)= 500 + (2 \times 150) =500+300= 500 + 300

800\boxed{₹800}

At the end of the 3rd month: =500+(3×150)= 500 + (3 \times 150) =500+450= 500 + 450

950\boxed{₹950}

At the end of the 4th month: =500+(4×150)= 500 + (4 \times 150) =500+600= 500 + 600

1100\boxed{₹1100}

Diagram 1

Step 2 — Find the linear expression

We can see a pattern in the calculations. The initial amount is ₹500. The pocket money is ₹150 per month. For nn months, she gets n×150n \times 150.

Let AnA_n be the amount in the nthn^{\text{th}} month. An=Initial amount+(Number of months×Pocket money)A_n = \text{Initial amount} + (\text{Number of months} \times \text{Pocket money}) An=500+(n×150)A_n = 500 + (n \times 150) An=500+150nA_n = 500 + 150n

An=150n+500\boxed{A_n = 150n + 500}

Answer

(i) At the end of the 2nd month, she will have ₹800. (ii) At the end of the 3rd month, she will have ₹950. (iii) At the end of the 4th month, she will have ₹1100. (iv) The linear expression for the nthn^{\text{th}} month is An=150n+500A_n = 150n + 500.

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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