Solve for 17 Exam Questions: Finding Distribution Across 3 Parts

Linear Equations with Multiple Variable Relationships

A theory exam consists of 17 questions and is divided into three parts.

The second part has 3 fewer questions than the first part and the last part has half the number of questions as the first part.

How many questions are there in each part?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 How many questions are in each part?
00:03 Let's mark the number of questions in part 1 using the unknown X
00:06 Let's express the number of questions in other parts using X
00:10 Let's build an appropriate equation according to the given data
00:14 The sum of questions equals 17
00:18 Let's group terms
00:27 Let's arrange the equation so that one side has only the unknown X
00:31 Let's isolate X
00:39 Let's convert from number and fraction to fraction
00:44 Let's write division as multiplication by reciprocal
00:47 Let's divide 20 by 5
00:50 This is the solution for X
00:53 Let's substitute this solution to find the number of questions in each part

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

A theory exam consists of 17 questions and is divided into three parts.

The second part has 3 fewer questions than the first part and the last part has half the number of questions as the first part.

How many questions are there in each part?

2

Step-by-step solution

To solve the problem, follow these steps:

  • Define variable x x as the number of questions in the first part.
  • Express the number of questions in the second and last parts in terms of x x , which are x3 x-3 and x2\frac{x}{2} respectively.
  • Set up the equation for the total number of questions: x+(x3)+x2=17 x + (x - 3) + \frac{x}{2} = 17 .

Now, let's solve the equation:
Combine like terms:
x+x3+x2=17 x + x - 3 + \frac{x}{2} = 17
This simplifies to:
2x+x23=17 2x + \frac{x}{2} - 3 = 17 .

Clear the fraction by multiplying the entire equation by 2:
2(2x)+2(x2)2(3)=2(17) 2(2x) + 2\left(\frac{x}{2}\right) - 2(3) = 2(17) ,
which simplifies to:
4x+x6=34 4x + x - 6 = 34 .

Combine the terms:
5x6=34 5x - 6 = 34 .
Add 6 to both sides:
5x=40 5x = 40 .
Divide by 5 to solve for x x :
x=8 x = 8 .

The number of questions in the first part is 8.

To find the number of questions in the second part, calculate x3 x - 3 :
83=5 8 - 3 = 5 .

For the last part, calculate x2\frac{x}{2}:
82=4\frac{8}{2} = 4 .

In conclusion, there are 8 questions in the first part, 5 questions in the second part, and 4 questions in the last part.

Therefore, the solution to the problem is 8,5,4 8, 5, 4 .

3

Final Answer

8,5,4 8,5,4

Key Points to Remember

Essential concepts to master this topic
  • Variable Definition: Let x represent the first part to establish relationships
  • Equation Setup: Combine x + (x-3) + x/2 = 17 for total
  • Verification: Check that 8 + 5 + 4 = 17 questions total ✓

Common Mistakes

Avoid these frequent errors
  • Setting up separate equations for each part instead of one combined equation
    Don't create three different equations like x = first, y = second, z = third = confusing system! This makes the problem unnecessarily complex and often leads to wrong relationships. Always define one variable and express all parts in terms of that single variable.

Practice Quiz

Test your knowledge with interactive questions

Solve for x:

\( 2(4-x)=8 \)

FAQ

Everything you need to know about this question

Why do I use only one variable instead of three?

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Using one variable (x) makes the problem simpler! Since the second and third parts are defined in terms of the first part, you can express everything using just x.

How do I handle the fraction x/2 in the equation?

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Multiply the entire equation by 2 to clear the fraction. This gives you 4x+x6=34 4x + x - 6 = 34 , which is much easier to solve!

What if my answer gives a non-whole number of questions?

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Check your work! Questions must be whole numbers. If you get fractions, there's likely an error in your setup or calculations.

How do I know which part to call 'x'?

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Choose the part that other parts are compared to. Here, both the second and third parts are described in terms of the first part, so let x = first part.

Can I check my answer without substituting back?

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Yes! Add up your three answers: 8 + 5 + 4 = 17. Also verify the relationships: second part (5) is 3 less than first (8), and third part (4) is half of first (8).

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