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4 - how many times ?

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by alltimeacheiver » Fri Jul 01, 2011 5:41 am
it is 10 times in sequesnce of 1 to 100 then from 1 to 10,000 will be 1000 times. scenario of digit 4 to repeat again.
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by Frankenstein » Fri Jul 01, 2011 5:52 am
alltimeacheiver wrote:it is 10 times in sequesnce of 1 to 100 then from 1 to 10,000 will be 1000 times. scenario of digit 4 to repeat again.
No..This is incorrect. It appears more than 10 times.
4,14,24,...94 -->9(excluding 44)
40,41,42,...49 -->11(44 has two 4s).
This problem is a bit lengthy, counting all such numbers. I am sorry I wouldn't count all such numbers.
Last edited by Frankenstein on Sun Jul 03, 2011 9:49 pm, edited 1 time in total.
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by winniethepooh » Fri Jul 01, 2011 6:14 am
May any one, please!
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by goalevan » Sun Jul 03, 2011 8:05 pm
I interpret this problem as how many times a 4 will appear in any place of a four-digit number _ , _ _ _.

Thousands digit: appears in every digit from 4,000 to 4,999, this is 1,000 times.
Hundreds digit: appears 100 times (400-499) for each of the 10 thousands digits (including 0), this is 1,000 times.
Tens digit: appears ten times (40-49) for each of the 100 hundreds digits (including 0), this is 1,000 times.
Unit digit: appears one time for each of the 1,000 tens digits, this is 1,000 times.

My answer is 4,000.
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