Question

Peter has 10 different books. 7 of them are novels and 3 are comics. In how many ways can Peter arrange 7 books on a shelf with 5 novels on the left and 2 comics on the right.

my answer:
7C5 * 3C2 = 63

is it correct?
@ganeshie8

Answer 1

yes right !!

Answer 2

As far as what I remember, yes....

Answer 3

oh, thanks!
do you mind i post another question is this post?

Answer 4

was it for me ?

Answer 5

Another question:
In a class, 6 students are divided into 3 groups of 2 students each. In how many ways can the 3 groups be formed?

my answer:
6C2=15

i don't think it'll be a simple question.

Answer 6

@digitalmonk what?

Answer 7

first 2 students (for the 1st group) can be selected in 6C2 ways, when two students have been selected for next group 4C2, for next group 1 way
total ways = (6C2x4C2x1)/ 3!

Answer 8

for your first question the order that you arrange the books and comics matter so you should be using permutation and not combinations.

Answer 9

but arranging books can be repeated...isn't it?

Answer 10

the books are said to be different so any permutation will give a unique arrangement. Therefore you need permutations and not combinations.

Answer 11

oh my god @@

Answer 12

so what's the correct working step?

Answer 13

just replace C with P (replace the combination with a permutation)

Answer 14

really ... ? ok...thanks..

Answer 15

15120?!

Answer 16

but the three groups formed are identical, the according to the problem "the order" inside each group in not of importance !!

Answer 17

@digitalmonk i think 63 is the answer lol. We are correct?

Answer 18

The first question is asking for the number of "arrangements". This is a permutation.