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q.1) find number of 5 digit number in which digit are in ascending order.
asked in Combinatory by Active (2.2k points) | 85 views
for ascending, we need to avoid $0$, we cannot place it anywhere, so we're left with $9$ options,

So, we'll be choosing $5$ digits out of $9$,i.e. $^9C_5$

and after choosing there is only $1$ way to arrange them.

∴ Answer will be $^9C_5 \times 1 =  ^{9}C_5 = 126$
what about repetition of digits?
repetition not allowed
in question it is mention that we have to arrange in ascending order ,have you any such number in which digit is repeated but it's still in ascending order???

then it is non-decreasing order...

@srestha mam

i didn't ask for this particular question, i asked for generally, due to it's look more tough.. May anyone have any simple method?

in that case ans also be same

because , take any example

like 2235

arrangement done in 1 way only

no mam,

check this question

and should check the first link provided on the comment on the question

1 Answer

+1 vote
out of 1,2,3,4,5,6,7,8,9 pick any 5 digits. only one way to arrange them(ascending order). So, 9C5.
answered by Loyal (7.6k points)

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