+0  
 
0
106
3
avatar

How many ways are there to walk from P to Q by only taking steps to the right or up?

 

 Dec 19, 2019
 #1
avatar+109563 
+2

We have  two    sets  to  consider

 

(right  right   up    up   up  )    *   ( right right  right  right  up  up  up  )

 

We have   C(5,2)   ways to select  the positions for  "right"  in the first set  and  C (7,4)  ways to select the positions for "right"  in the second set

 

So....the total paths  are    C(5,2)  * C(7,.4)  =   10  * 35  = 350 possible  paths

 

[ Note....the same result  would be obtained  by choosing any C(5,3) and C(7,3)  positions for  "up"  in both sets ]

 

EDIT....THX TO THE GUESY FOR CATCHING MY ERROR  !!!!

 

cool cool cool

 Dec 19, 2019
edited by CPhill  Dec 19, 2019
 #2
avatar
0

wouldn't it be 7 chooose 4 instead of 8 chooose 5?

Guest Dec 19, 2019
 #3
avatar+109563 
+1

Yep....sorry....let me make an edit!!!

 

Thanks for  catching  that   !!!!

 

 

 

cool cool cool

CPhill  Dec 19, 2019

13 Online Users