# \[OFFICIAL\] Basic Math/Combinatorics Problems

**URL:** <https://discuss.codechef.com/t/official-basic-math-combinatorics-problems/65236>\
**Category:** CodeChef-DSA-learners\
**Tags:** basic, combinatorics, math\
**Created:** [May 10, 2020, 4:06am UTC](https://discuss.codechef.com/t/official-basic-math-combinatorics-problems/65236 "2020-05-10T04:06:09Z")\
**Posts on this page:** 1\
**Showing post:** 16

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**Author:** ![shameekagarwal](https://discuss.codechef.com/user_avatar/discuss.codechef.com/shameekagarwal/32/3653_2.png) [@shameekagarwal](https://discuss.codechef.com/u/shameekagarwal)\
**Post date:** [August 29, 2020, 12:24pm UTC](https://discuss.codechef.com/t/official-basic-math-combinatorics-problems/65236/16 "2020-08-29T12:24:30Z")

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**can u please explain 2 c)**

**also 1 b) (i got the same answer just want to know approach)**

my 1b) -

(n+1 ‘R’) (1 ‘L’) (m ‘U’) but ‘L’ cant come first or last - so only n/(n+2) cases valid

```auto
    (n + m + 2)! n
    ------------ * -----
    (n + 1)! m! (n + 2)

```

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