IIT JEE , AIEEE Forum - Mathematics , Algebra

sharmadon

in an examination in an objective test there are two sections containing 10 questions each.In section 1,each objective question has 5 choices and only one choice is correct.Section 2 has 4 choices for each question and more than one choice may be correct.Marks for section 2 is awarded only if a student gives all choices correct.There is no negative marking for any section.For each question in section1 and section 2, 1 and 3 marks are will be awarded respectively.

1. if a student attempts only two questions,one from section 1 and the other from section 2, then what is the probability that he is awarded marks in both questions?

2.what is the probability of getting marks less than 40 for a student ?

3. if a student attempts 4 questions, 2 from each section,then what is the probability that he gets 4 marks ?

4.if a student attempts all the questions then what is the probability that he gets 5 marks in section 1 and 15 in section 2?

computer001

EDITED:

1)1/5 * 1/15

2) 1-{(1/5)^10}*{(1/15)^10}

3)(1/5)*(1/15)*(14/15)*(4/5)*4

4)10C5*(1/5)^5*(4/5)^5*10C5*(1/15)^5*(14/15)^5

supralara

1)1/5 * 1/15

2) 1-{(1/5)^10}*{(1/15)^10}

3)(1/5)*(1/15)*(14/15)*(4/5)*4

4)¹⁰C₅*(1/5)^5*(4/5)^5*¹⁰C₅*(1/15)^5*(14/15)^5

layman

what's the point in repeating answers?

sandeepramesh

4)¹⁰C₅*(1/5)^5*(4/5)^5*¹⁰C₅*(1/15)^5*(13/15)^5

that was changed

layman

Atleast for the first three parts

computer001

MR.LAYMAN:
diff ppl diff thinkin ..diff soln..

layman

Ya, then post ur methods atleast. Then we say the method's are different.

computer001

MR LAYMAN

IT TAKES A WHOLE LOT OF TIME TO TYPE IT OUT...N ITS DIRECT.. SO NO POINT IN POSTIN THE FULL SOLUTION

computer001

@ supralara:
pl if u edit an answer say: "EDITED"

layman

Ya I agree then what's the point in repeating the answers computer001

computer001

WELL MAYB ME OR SUPRALARA PLAN TO POST THE SOLN LATER..TILL THEN THIS SHUD SUFFICE.. IL MAKE SURE I NUDGE U IF I POST IT..IF U WANNA SEE DIVERSITY IN PROBLEM SOLVING SO BADLY..

layman

Don't get too irritated computer001.

sharmadon

there is a point in posting the answers...

the one who is asking doesnt know the way..at least give me hints...so please try posting the hints..or do one thing...click a picture of ur solutions and post it..or mail them to me...

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