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8 Digit Landline Number
Total 5 Digit Telephone Numbers - Permutations & Combinations Question
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now let's learn another question
completely based on the fundamental
principle of counting and the question
is how many five digit telephone number
do you in mind that that's a refi busy
telephone number can be constructed
using the digits 0 to 9
okay zero to nine digits can be used if
the each number starts with successive M
that is this is also very very important
starts with six and seven and no digits
appears more than once means reputation
is not allowed cool so let's get it
straight to the question question is
saying we have to make five digit
telephonic numbers so I have five places
one two three four five all right and
the options that I can feel you are here
ten digits zero one two three four five
six seven eight nine all right so there
are ten digits with which I'm going to
make five digit telephonic number and
one thing one thing one thing the
question has already given some
restrictions the telephone number each
numbers which starts with 67 alright so
67 6 7 so first should be 6 and seconds
would be 7 so this is fixed all right so
6 and 7 let me cancel now alright so
this is already blocked all right we
cannot walk out here so there are only
now 3 positions left for us to work out
all right so this position can be filled
by any of the rest element we can fill
this with 0 by 1 or by 2 or by 3 or by 4
or by 5 or by 8 or by 9 alright so how
many options we have 1 2 3 4 5 6 7 8 so
by the 8 different numbers we can fill
this one alright and if we feel this
then one will get sorted this for a
while let's say we feel this by zero for
a while this time supposing we filled
with zero so now we have two different
places to be filled with rest of the
numbers we can fill this either by one
or by two or by 3 or by 5 or by 5 or by
8 or by 9 so options are 1 2 3 4 5 6 7
so there are several options to fill
this one and once you will fill this one
more we'll get to shortage let's say we
fill with 9 for a while and now we're
left to fill one position with rest of
element so to fill this last position we
can choose any one of them we can choose
one we can choose two we can choose
three you can choose four we can choose
five you can choose 8 so options are 1 2
3 4 5 6 all right 6 so the total 5
detail for
then we can prepare that it starts with
67 R now this will work as a 1 alright
and it is going to fill with eight ways
this can fill with seven way this can be
filled with six weeks so total will be
now 8 times 7 times 6 336 so we can
prepare 336 5dg telephonic number that
starts with 67 and contains the numbers
from 0 to 9 when repetition is not a lot
when digits once appears is not going to
appear once again
