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In a test of 50 questions, each correct answer fetches two marks and each wrong answer fetches \(-1 / 2\) marks. A candidate attempted all the questions and scored 40 mark. How many questions did he attempt correctly? (1) 24 (2) 26 (3) 22 (4) 20

Short Answer

Expert verified
Answer: 26

Step by step solution

01

Define the variables

Let x be the number of correct answers and y be the number of wrong answers. Since the candidate attempted all 50 questions, we can write the equation: x + y = 50
02

Use the given information to form another equation

According to the information given, each correct answer fetches 2 marks, and each wrong answer fetches \(-1 / 2\) marks. The total marks scored are 40. So the equation becomes: 2x - \(\frac{1}{2}\)y = 40
03

Solve the system of equations to find the value of x

Now we have a system of two equations with two variables: 1) x + y = 50 2) 2x - \(\frac{1}{2}\)y = 40 We'll solve the equation 1 for y, then substitute the result in equation 2: y = 50 - x Now substitute this into the second equation: 2x - \(\frac{1}{2}\)(50 - x) = 40
04

Solve the equation for x

Now, we will solve this equation for x. 2x - 25 + \(\frac{1}{2}\)x = 40 Combine like terms: \(\frac{5}{2}\)x - 25 = 40 Now, isolate x by adding 25 to both sides and then multiplying by \(\frac{2}{5}\): \(\frac{5}{2}\)x = 65 x = \(\frac{2}{5}\)(65) x = 26
05

Conclusion

Since the value of x is 26, the candidate answered 26 questions correctly. So, the correct answer is (2) 26.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

System of Equations
Understanding how to navigate a system of equations is pivotal in algebra, especially when dealing with real-world scenarios such as test scoring. A system comprises two or more equations with a common set of variables. In the exercise, the system consists of two equations with variables representing the number of correct and incorrect answers.

To solve the system, we often use methods like substitution or elimination. Here we used substitution, which is practical when one equation can be easily isolated in terms of one variable. After finding an expression for one variable, we substitute it into the other equation. Solving a system accurately not only leads to the right answer but also enhances problem-solving skills which are adaptable to various mathematical situations.
Problem-Solving
Strong problem-solving skills are essential in mathematics to break down complex scenarios. The textbook exercise required interpreting the test conditions to form mathematical expressions. This involves reading the problem carefully, identifying the variables, and translating the words into algebraic equations.

Effective problem-solving includes checking whether solutions make sense in the context of the problem. For instance, we wouldn’t expect a negative number of correct answers. This contextual understanding is as critical as the algebraic manipulation in ensuring the solution is not only mathematically correct but also logically consistent.
Algebra
The principles of algebra are crucial to manipulating and solving equations. This exercise showcases basic algebraic techniques such as isolating variables and combining like terms. In the step-by-step solution, terms with 'x' were combined to help isolate the variable, a technique that simplifies equations and leads to the variable’s value.

Understanding these techniques is vital for students as algebra acts as the foundation for much of higher mathematics. It's not just about finding the right answer but also about understanding the 'why' and the 'how' of the operations we perform. Continued practice in these areas can lead to greater mathematical proficiency and confidence.
Test Scoring
When we consider test scoring in the context of mathematics, we often come across problems where the scoring system must be analyzed and interpreted to find a result. In this exercise, we had to understand the scoring rules to set up the right equations.

The practical application in this case teaches students the importance of weightage given to correct versus incorrect answers. It grasps the concept of negative marking and how it can impact the total score. In a real-world scenario, this understanding is crucial not just for solving such problems but also for strategizing how to attempt a test to maximize the final score.

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