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Finding The

🎓 Class 7📖 Ganita Prakash-II📖 8 notes🧠 15 Q&A⏱️ ~12 min
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Finding TheStudy Notes

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Introduction

Explanation

Introduction

In this chapter, 'Finding the Unknown,' we explore the fundamental concept of solving equations to find unknown quantities. The chapter introduces the idea that in many real-life situations, we come across problems where certain values are unknown and need to be determined using given information. These unknowns are represented by variables, usually denoted by letters such as x, y, or z. The process of finding these unknown values is called solving an equation. An equation is a mathematical statement that shows the equality of two expressions, often involving variables and numbers. The chapter emphasizes that solving equations is a crucial skill in mathematics and daily life, enabling us to solve problems related to age, money, distance, and many other areas. It also introduces the concept of balancing both sides of an equation to maintain equality and find the value of the unknown. This foundational knowledge prepares students for more complex algebraic manipulations in higher classes.

  • Unknown quantities in problems are represented by variables.
  • An equation shows equality between two expressions.
  • Solving an equation means finding the value of the unknown variable.
  • Maintaining balance on both sides of the equation is essential.
  • Equations are used to solve real-life problems involving unknowns.
  • Understanding equations is foundational for algebra.
  • 📌 Variable: A symbol (usually a letter) used to represent an unknown number.
  • 📌 Equation: A mathematical statement showing equality between two expressions.
  • 📌 Solving an equation: Finding the value of the variable that makes the equation true.

What is an Equation?

Definition

What is an Equation?

An equation is a mathematical statement that asserts the equality of two expressions. It contains two expressions separated by an equal sign (=). For example, 3 + x = 7 is an equation where x is the unknown variable. The chapter explains that equations are like a balance scale where both sides must be equal. If one side changes, the other side must also change to maintain equality. The unknown variable represents a number that makes the equation true when substituted. The chapter also distinguishes between expressions and equations: an expression is a combination of numbers and variables without an equal sign, while an equation includes an equal sign and shows equality. Understanding this difference is crucial for solving problems. The section introduces the concept of the solution of an equation, which is the value of the variable that satisfies the equation. The chapter encourages students to check their solutions by substituting the value back into the equation to verify equality.

  • An equation contains two expressions separated by an equal sign.
  • Expressions do not have an equal sign; equations do.
  • The unknown variable is the number to be found.
  • The solution of an equation is the value that satisfies it.
  • Equations represent balanced relationships.
  • Checking the solution by substitution is important.
  • 📌 Expression: A combination of numbers and variables without equality.
  • 📌 Equation: A statement showing equality between two expressions.
  • 📌 Solution of an equation: The value of the variable that makes the equation true.

Properties of Equality

Concept

Properties of Equality

This section introduces the fundamental properties of equality that help in solving equations. The two main properties are the Addition Property of Equality and the Multiplication Property of Equality. The Addition Property states that if the same nu

Practice QuestionsFinding The

Includes NCERT exercise questions with answers

Q1.We have the expression 3k + 1 which gives the number of tiles needed to make an arrangement in Step k. To check whether an arrangement is possible using 100 tiles at some Step k, we can solve the equation: 3k + 1 = 100. Find the value of k.

Answer:

Given the equation 3k + 1 = 100, Subtract 1 from both sides: 3k = 100 - 1 3k = 99 Divide both sides by 3: k = 99 ÷ 3 k = 33 Therefore, the arrangement using 100 tiles corresponds to Step 33.

Explanation:

The expression 3k + 1 represents the number of tiles at Step k. To find k for 100 tiles, solve 3k + 1 = 100. Subtract 1 to isolate 3k, then divide by 3 to find k.

EasyNCERT
Q2.Madhubanti wants to organise a party. She decides to buy snacks for the party from the chaat shop in town. Each plate of snacks costs ₹25. The shop charges an additional fixed amount of ₹50 to deliver the snacks to Madhubanti’s house. There are 5 members in Madhubanti’s family, including herself. Her parents tell her she can spend ₹500 on this party. How many friends can she invite to the party if she wants to give a plate of snacks to each person, including her family and friends?

Answer:

Total money available = ₹500 Delivery charge = ₹50 Money left for snacks = 500 - 50 = ₹450 Cost per plate = ₹25 Number of plates that can be bought = 450 ÷ 25 = 18 Number of family members = 5 Number of friends invited = 18 - 5 = 13 Therefore, Madhubanti can invite 13 friends.

Explanation:

Subtract the fixed delivery charge from total money to find amount left for snacks. Divide this by cost per plate to find total plates. Subtract family members to find number of friends.

EasyNCERT
Q3.Two friends want to save money. Jahnavi starts with an initial amount of ₹4000, and in addition, saves ₹650 per month. Sunita starts with ₹5050 and saves ₹500 per month. After how many months will they have the same amount of money?

Answer:

Let m be the number of months after which their savings are equal. Jahnavi's savings after m months = 4000 + 650m Sunita's savings after m months = 5050 + 500m Set equal: 4000 + 650m = 5050 + 500m Subtract 500m from both sides: 4000 + 150m = 5050 Subtract 4000 from both sides: 150m = 1050 Divide both sides by 150: m = 1050 ÷ 150 = 7 Therefore, after 7 months, both will have the same amount of money.

Explanation:

Set the expressions for savings equal and solve for m by isolating the variable step-by-step.

MediumNCERT
Q4.Solve 28 (x + 4) + 300 = 1000.

Answer:

Given equation: 28(x + 4) + 300 = 1000 Step 1: Subtract 300 from both sides: 28(x + 4) = 1000 - 300 28(x + 4) = 700 Step 2: Divide both sides by 28: x + 4 = 700 ÷ 28 x + 4 = 25 Step 3: Subtract 4 from both sides: x = 25 - 4 x = 21 Therefore, the solution is x = 21.

Explanation:

Isolate the term with x by subtracting 300, then divide by 28 to solve for x + 4, and finally subtract 4 to find x.

EasyNCERT
Q5.Riyaz created a math trick, which he tries out on his friend Akash. Riyaz asked Akash to perform the following steps without revealing the answer to any of the intermediate steps. 1. Think of a number. 2. Subtract 3 from the number. 3. Multiply the result by 4. 4. Add 8 to the product. 5. Reveal the final answer. The final answer revealed by Akash was 24. Using this, Riyaz correctly figured out the starting number that Akash had thought of. Find this number.

Answer:

Let the starting number be x. Step 2: x - 3 Step 3: 4(x - 3) = 4x - 12 Step 4: 4x - 12 + 8 = 4x - 4 Given final answer = 24 So, 4x - 4 = 24 Add 4 to both sides: 4x = 24 + 4 = 28 Divide both sides by 4: x = 28 ÷ 4 = 7 Therefore, the starting number is 7.

Explanation:

Translate each step into an algebraic expression, form an equation with the final answer, and solve for the unknown starting number.

EasyNCERT
Q6.What is an equation in mathematics?
A.A) A mathematical statement showing equality between two expressions
B.B) A combination of numbers and variables without an equal sign
C.C) A number without any variables
D.D) A statement involving only addition

Answer:

A mathematical statement showing equality between two expressions

Explanation:

An equation is a mathematical statement that asserts the equality of two expressions separated by an equal sign. It involves variables or numbers and shows that both sides have the same value.

Easy
Q7.Which of the following is NOT an equation?
A.A) 3x + 4 = 7
B.B) 5 + y = 12
C.C) 2x + 3
D.D) a = 50

Answer:

2x + 3

Explanation:

An equation must have an equal sign showing equality between two expressions. '2x + 3' is an expression without an equal sign, so it is not an equation.

Easy
Q8.If the equation is $2n + 1 = 99$, what is the value of $n$?
A.A) 49
B.B) 50
C.C) 48
D.D) 51

Answer:

49

Explanation:

Given the equation 2n + 1 = 99, subtract 1 from both sides: 2n = 98. Divide both sides by 2: n = 49.

Medium