AdrenalineX Forums
General => Off-Topic => Topic started by: AdrenalineXV on April 23, 2015, 02:32:43 am
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Question 1:
With the digits 7, 3, 5, 6; 24 four-digit numbers can be formed. From these 24 numbers, the quantity of odd numbers is the same as a:
So, I know that 4! / (4-4)! = 24. There are 3 odd numbers and one even number. What is next?
Regards.
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I'm so confused.
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I'm so confused.
mooman, Agus:
It is the same as above: If 24 numbers (four-digit each one) can be formed with: 7, 3, 5 ,6. Find the quantity of odd numbers from these.
Regards.
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Anything multiplied by 10, 100 or 1000 is even and adding an even number to an odd/even number results in an odd/even number. Therefore only the last digit matters and every number will be odd except for those ending in 6, of which there are 3! = 6.
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Anything multiplied by 10, 100 or 1000 is even and adding an even number to an odd/even number results in an odd/even number. Therefore only the last digit matters and every number will be odd except for those ending in 6, of which there are 3! = 6.
Ok mooman, I have got your point. Now: 7, 3, 5, 6. There are 3 odd numbers, that means that just 3 of four numbers can be used to get a four-digit odd number; so: 3 out of four numbers.
3 possibilities will be multiplied for the rest of available digits: 3*3*2*1 = odd numbers.
1 possibility will be multiplied in order to get the total of even numbers: 1*3*2*1 = even numbers.
Thanks.
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