JEE MAIN - Mathematics (2002 - No. 48)
Five digit number divisible by 3 is formed using 0, 1, 2, 3, 4 and 5 without repetition. Total number of such numbers are :
312
3125
120
216
Explanation
Note : For a number to be divisible by 3, the sum of digits should be divisible by 3.
Here given numbers are 0, 1, 2, 3, 4 and 5. Out of those 6 numbers possible sets of 5 numbers are (1, 2, 3, 4, 5) and (0, 1, 2, 4, 5) whose sum are divisible by 3.
Set 1 : Set is = (1, 2, 3, 4, 5). Sum of digits = 1 + 2 + 3 + 4 + 5 = 15 (Divisible by 3)
So total no of arrangement = 1$$ \times $$2$$ \times $$3$$ \times $$4$$ \times $$5 = 5!
Set 2 : Set is = (0, 1, 2, 4, 5). Sum of digits = 0 + 1 + 2 + 4 + 5 = 12 (Divisible by 3)
So total no of arrangement = 4$$ \times $$4$$ \times $$3$$ \times $$2$$ \times $$1 = 4.4!
$$\therefore$$ Total arrangement = 5! + 4.4! = 216
Here given numbers are 0, 1, 2, 3, 4 and 5. Out of those 6 numbers possible sets of 5 numbers are (1, 2, 3, 4, 5) and (0, 1, 2, 4, 5) whose sum are divisible by 3.
Set 1 : Set is = (1, 2, 3, 4, 5). Sum of digits = 1 + 2 + 3 + 4 + 5 = 15 (Divisible by 3)

So total no of arrangement = 1$$ \times $$2$$ \times $$3$$ \times $$4$$ \times $$5 = 5!
Set 2 : Set is = (0, 1, 2, 4, 5). Sum of digits = 0 + 1 + 2 + 4 + 5 = 12 (Divisible by 3)

So total no of arrangement = 4$$ \times $$4$$ \times $$3$$ \times $$2$$ \times $$1 = 4.4!
$$\therefore$$ Total arrangement = 5! + 4.4! = 216
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