Answer
451.2k+ views
Hint – try to solve these questions with the help of linear equations and compare them both.
Complete step-by-step solution -
According to the question, let the right answer be $x$ and the number of wrong questions as $y$
Now as per the question,
$
\Rightarrow 3x - y = 40....\left( i \right) \\
\Rightarrow 4x - 2y = 50....\left( {ii} \right) \\
$
Now multiplying $\left( i \right)$ by $\left( {2} \right)$ and subtracting $\left( {ii} \right)$ from $\left( i \right)$ will get,
$
\Rightarrow 6x - 2y - 4x + 2y = 80 - 50 \\
\Rightarrow 2x = 30 \\
\Rightarrow x = 15 \\
$
Now putting in $x$ in $\left( i \right)$ will get,
$
\Rightarrow 3 \times 15 - y = 40 \\
\Rightarrow 45 - y = 40 \\
\Rightarrow - y = 40 - 45 \\
$
Now cancelling out the same signs we will get,
$y = 5$
So correct answer $ = 15$, wrong answer $ = 5$
Total question $ = x + y = 15 + 5 = 20 $ questions
So, the option “A” is correct.
Note- Use of linear equations in solving such questions will be helpful. In mathematics, a linear equation is an equation that may be put in the form where the variables are, and are the coefficients, which are often real numbers. The coefficients may be considered as parameters of the equation, and may be arbitrary expressions, provided they do not contain any of the variables.
Complete step-by-step solution -
According to the question, let the right answer be $x$ and the number of wrong questions as $y$
Now as per the question,
$
\Rightarrow 3x - y = 40....\left( i \right) \\
\Rightarrow 4x - 2y = 50....\left( {ii} \right) \\
$
Now multiplying $\left( i \right)$ by $\left( {2} \right)$ and subtracting $\left( {ii} \right)$ from $\left( i \right)$ will get,
$
\Rightarrow 6x - 2y - 4x + 2y = 80 - 50 \\
\Rightarrow 2x = 30 \\
\Rightarrow x = 15 \\
$
Now putting in $x$ in $\left( i \right)$ will get,
$
\Rightarrow 3 \times 15 - y = 40 \\
\Rightarrow 45 - y = 40 \\
\Rightarrow - y = 40 - 45 \\
$
Now cancelling out the same signs we will get,
$y = 5$
So correct answer $ = 15$, wrong answer $ = 5$
Total question $ = x + y = 15 + 5 = 20 $ questions
So, the option “A” is correct.
Note- Use of linear equations in solving such questions will be helpful. In mathematics, a linear equation is an equation that may be put in the form where the variables are, and are the coefficients, which are often real numbers. The coefficients may be considered as parameters of the equation, and may be arbitrary expressions, provided they do not contain any of the variables.
Recently Updated Pages
How many sigma and pi bonds are present in HCequiv class 11 chemistry CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Why Are Noble Gases NonReactive class 11 chemistry CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Let X and Y be the sets of all positive divisors of class 11 maths CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Let x and y be 2 real numbers which satisfy the equations class 11 maths CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Let x 4log 2sqrt 9k 1 + 7 and y dfrac132log 2sqrt5 class 11 maths CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Let x22ax+b20 and x22bx+a20 be two equations Then the class 11 maths CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Trending doubts
Fill the blanks with the suitable prepositions 1 The class 9 english CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
At which age domestication of animals started A Neolithic class 11 social science CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Which are the Top 10 Largest Countries of the World?
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Give 10 examples for herbs , shrubs , climbers , creepers
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Difference between Prokaryotic cell and Eukaryotic class 11 biology CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Difference Between Plant Cell and Animal Cell
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Write a letter to the principal requesting him to grant class 10 english CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Change the following sentences into negative and interrogative class 10 english CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)
Fill in the blanks A 1 lakh ten thousand B 1 million class 9 maths CBSE
![arrow-right](/cdn/images/seo-templates/arrow-right.png)