3-अंक की कितनी धनपूर्ण संख्याएँ (अंकों का प्रयोग दुबारा किए बिना) इस प्रकार होंगी कि संख्या का प्रत्येक अंक विषम हो और संख्या 5 से विभाज्य हो?

Correct Answer: (B) 12

The available odd digits are $\{1, 3, 5, 7, 9\}$. For a number to be divisible by 5 and have all odd digits, its unit digit must be 5. With 5 fixed in the units place, the hundreds place can be filled by any of the 4 remaining odd digits $\{1, 3, 7, 9\}$, and the tens place can then be filled by any of the remaining 3 odd digits without repetition. Thus, there are $4$$\times$ 3 = 12 such numbers.