Q.

Number of odd integers between 1000 and 8000 which have none of their digits repeated is

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a

690

b

1014

c

810

d

1736

answer is D.

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Detailed Solution

  1. For a number to be odd the digit in  units place should be 1,3,5,7,9

case(1)

Let the units  place is filled with 9

Since the required number is less than 8000

first place canot be filled with o,8,9.

So thousands place can be filled using digits from 1 to 7

and remaining two places can be filled in 8.7 ways
Then we have 7.8.7=392 

case (2)
If the units place is filled using 1,3,5,7 then

thousands place can be filled in 6 ways

middle two places in 8.7 ways
We have (6)(8)(7)(4)=1344, (0,9( or )8)can not come at thousands place.
Total 392+1344=1736 .

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