Question

I was to give one Mark for every sum right and to deduct one Mark for every sum wrong. after working on 36 sums the total
marks equal led to 4. how many sums had been done correctly?

Answer 1

Given:

Total marks obtained is 4.

To find:

The number of the correct questions.

Solution:

1) The total number of the attempted question is 36.

2) If all the questions are correct then the marks obtained would be 36.

3) If all the questions are wrong then the marks obtained would be -36.

4) By the concept of the mixture allegation

    Right               :                 Wrong

    36                                        -36

                           4

    40                                         32

• Right: Wrong = 5:4

total ratio for the attempted question is 9.

• 9 ---- 36 questions.

• 1 ----- 4 questions.

• 5 ----- 20 questions.

The total number of the right questions are 20.