What is the number of odd integers between 1000 and 9999 with no digit...
Case I
When unit digit can be 1,3,5 or 7 & digit at thousand’s place can be 1,2,3,4,5,6,7 or 8.
No. of ways digits can be filled are:
Total no’s = 7 * 8 x 7 x 4 = 1568.
Case II
When unit digit can be 9 & digit at thousand’s place can be 1,2,3,4,5,6,7 or 8.
No. of ways digits can be filled are:
Total no’s = 8 x 8 x 7 x 1 = 448.
CaseIII
When unit digit can be 1,3,5 or 7 & digit at thousand’s place can be 9.
No. of ways digits can be filled are:
Total no’s = 1 x 8 x 7 x 4 = 224.
∴ Number of odd digits between 1000 & 9999 with no digit repeated = 1568 + 448 + 224 = 2240.