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q.1) find number of 5 digit number in which digit are in ascending order.
+5
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 $^9C_5 \times 1 = ^{9}C_5 = 126$
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repetition not allowed
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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???
+1
@BASANT

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?
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@Shaik

in that case ans also be same

because , take any example

like 2235

arrangement done in 1 way only
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no mam,

check this question https://gateoverflow.in/8399/gate2015-3-5

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

+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 ago by Active (1.9k points)