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How many 4-digit numbers have the second digit even and the fourth digit at least twice the second digit?

wiskdls  Apr 24, 2018
 #1
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OOps....was out on a run with the doggies and realized I made a mistake here...it is now corrected...

We have 9 possibilities for the first digit

The Third digit can be 0-9 (ten possibilities)

Three possible for the second digit   0 2 4

with 0    9 of the digits (1-9) can be fourth digit

 with 2   the fourth digit can be 4 5 6 7 8 9 (six possibilities)

  and with 4   only  8 9 can be fourth digit       ( 6 or 8 cannot be the second digit because fourth needs to be 2x)

 

       0                           2                         4

9  * 1 * 10 * 9     +  9 * 1 * 10 * 6   +  9 * 1 *10 * 2  =   Well, I think you can do this math !

Guest Apr 25, 2018
edited by Guest  Apr 25, 2018
edited by Guest  Apr 25, 2018
edited by Guest  Apr 25, 2018
edited by Guest  Apr 25, 2018
edited by Guest  Apr 25, 2018

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