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shalini goyal Grade: 12
        

a flight of stairs has 10 steps.a person can go up the steps one at a time ,two at a time,or any combination of 2's and 2's.find d total number f wayz in which d person can go up d stairs??? plz give me complete soln for dis....cuz i got d ans bt prob z m nt sure about the way i solved it!! ans is:89
do reply....plzz!!

6 years ago

Answers : (1)

AskiitiansExpert Mohit-IITD
21 Points
										

Dear Shalini,


There are 10 steps, so following cases are possible:


10 single steps =1


1 double steps, 8 single steps = 9!/8! =9


2 double steps, 6 single steps = 8!/6!2!=28


3 double steps, 4 single steps = 7!/4!3!=35


4 double steps, 2 single steps = 6!/4!2!=15


5 double steps = 1


Total=89


Hope this helps.


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6 years ago
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