In an exam total 15 questions are asked. You have to give answer of any 12 questions. Questions are

M4maths Previous Puzzles

09 Sep 2011 examination

In an exam total 15 questions are asked. You have to give answer of any 12 questions. Questions are divided in 3 sections. Each section contains 5 questions. You have to solve at least 3 questions from each section. How many methods are possible to give answers of all 12 questions.

OPtion

1) 256
2) 260
3) 275
4) 294
5) 308
6) 340
7) 395
8) 425
9) 505
10) none of these

Solution

Two cases arise
1) solve 3,4 and 5 questions from sections
total methods = 6*(5*4/2*1)*(5/1)*(1)= 300
2) sole 4 from each section
total methods = 5*5*5 =125
so answer = 300+125 = 425

Correct Option: 8 Best Solution (4)

vignesh s p   13 years AGO

the combinations are 345,453,534,354,435,543,444 from each sections(answers to be written). the combination (5c3*5c4*5c5)=50. therefore 50*6=300 & combination of 444 is (5c4*5c4*5c4)=125. hence 300+125=425

Like? Yes (6) | No (1)  

kalirathinam   13 years AGO

we have to answer for atleast 3 ques in section.
so the minimum no of ques to answer is 3. the maximum no is 5.
if we answer 4 ques in each section, the chances to answer are =(5c4*5c4*5c4)
so the total chances to answer the 12 ques are
= (5c4*5c4*5c4)+(5c4*5c3*5c5)+(5c5*5c4*5c3)+(5c4*5c5*5c3)+(5c5*5c3*5c4)+(5c3*5c4*5c5)+(5c3*5c5*5c4)
= 425
answer is option 8

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harikrishnan   13 years AGO

ans is

we can chose 4 ques from each section 0r
can select 5 frm 1st sec 4 frm 2nd 3 frm 3rd so that to answer 12 ques
there is only one way to chose 4*4*4 ques hence no of combination in this 1*(5c4*5c4*5c4)
and there are 6 combinations to chose 5*4*3 ques hence no of combination inthis way 6*(5c5*5c4*5c3)
total num of ways =1*(5c4*5c4*5c4)+6*(5c5*5c4*5c3)
= 1*(5*5*5) + 6*(1*5*10)
= 425

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Dhandayuthapani   13 years AGO

ans 405 .. 4 4 4 and 3 4 5 4 5 3 5 3 4 combination

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