Question

in a test +3marks are given for every correct answer and-1marks are given for every incorrect answer .sona attempted all the questions and scored +20marks though she got 10 correct answers how many incorrect answers has she attempted? how many questions were given in the test

Answer 1

Let x = number correct,  then 20 - x = number incorrect

 

Then, 5x - 2(20-x) = 51

 

         5x - 40 + 2x = 51

 

               7x - 40 = 51

 

                     7x = 91

 

                      x = 13

mark. it as brainliest

Answer 2

Let no. of correct answers be x
and no. of incorrect ans be y 

We are given, 3x - y  = 20 .............................(1)
                     so, x = 20+y/3

so, if she attempted 10 correct  ans.
Then x = 10

so, 10 = 20+y/3        [By (1)]
 so, y = 10

Hence, incorrect ans = 10 

So, total no of questions [if incorrect ans = 10] = x+y = 10+10 = 20