Thursday, December 13, 2012

number game

i did post a probability question before here so now let's play another number game.

in a test, there are 50 true or false questions. if a student manage to get only 17 questions right and wrong for the rest, his score will only be 1%. how many questions that student need to get right if he answers all the questions in order to pass the test given that the passing mark is 50%.

I'm not gonna bother to ask about the probability here as we already knew no matter what marks we want to get that the answer will always be 50% for true or false question.

oh btw, I do ponder whether the act of the student reading the questions do affect the marks that they will get instead of them guessing the answer blindly without even reading the questions at all. will one have a possibility to get higher marks if one reads the questions? I'd like to do a test for this one but i dont think that i can do it since im doing medic now. it's just a simple test but, oh well......

1 comment:

  1. so here's the answer for this q.
    let a be the no. of right answer while b is the no. of wrong answer.
    let x be the marks you get when answering right question and y marks you get when answering wrong question.

    so from here we have
    a + b = 50
    ax + by = marks, 17x + 33y = o.5 (1% out of 50 is 0.5)
    if the student get all the question right he surely get 100% so 50x = 50 which means x is 1

    so y = (0.5-17)/33 = -0.5

    in order to pass the exam which is getting 50% the least, a - 0.5(50-a) =/> 25
    a =/> 33.333. so the students need to get at least 34 questions right in order to pass the test given that the student answers all 50 questions.