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UPSC Prelims

Mathematics

Theme:

Number System / संख्या पद्धति

Q18 2022, Number System

How many 3-digit natural numbers (without repetition of digits) are there such that each digit is odd and the number is divisible by 5?

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?

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Each digit is odd and number is divisible by 5 means the unit digit would be 5 (and not zero).

So, the number will be in the form ‘xy5’.

For the value of x and y we use remaining odd digits (1, 3, 7, 9) which can happen in 4 × 3 = 12 ways (as repetition of digits is now allowed).
Thus there will be 12 such numbers.

व्याख्या Please wait..

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