Algebra> permutations-and-combinations...

A student is to answer 10 out of 13 ques. ,an examination such ythat he must choose at least 4 from the first 5 ques. The no. of choices available to him is-

Vaibhav , 11 Years ago

Grade 11

4 Answers

shubham sharma

Last Activity: 11 Years ago

its 196

from 1st 5 he can choose 4 or5 questions so

5C4.8C6 + 5C5.8C5

Approved

jitender lakhanpal

Last Activity: 11 Years ago

there would be two cases

1) when 4 is selected from first five and rest 6 from remaining 8

we can do it by 5C4 * 8C6

2) when all 5 are selected from first 5 and rest 5 from remaining 8

5C5 * 8C5

add both of them you will get the answer

We are all IITians and here to help you in your IIT JEE preparation.

Now you can win by answering the questions on Discussion Forum. So help discuss any query on askiitians forum and become an Elite Expert League askiitian.

Now you score 5+15 POINTS by uploading your Pic and Downloading the Askiitians Toolbar : Click here to download the toolbar..

Thanks and Regards

Jitender

(askIITians expert)

Shubham Nikat

Last Activity: 5 Years ago

Why 5C4×9C6 is not giving the correct answer. As the student can choose any four out of the first five questions. Then the one left out of this selection and other remaining 8 questions makes available 9 choices for selecting another 6 questions.

Rishi Sharma

Last Activity: 4 Years ago

Dear Student,
Please find below the solution to your problem.

there would be two cases
1) when 4 is selected from first five and rest 6 from remaining 8
we can do it by 5C4 * 8C6
2) when all 5 are selected from first 5 and rest 5 from remaining 8
5C5 * 8C5
add both of them you will get the answer

Thanks and Regards