How many 4 digits number have all their digits either even ir odd?
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Hey!
1. ODD
If we want that all 4 digits are odd,then the selection for all four places can be done from 1,3,5,7,9. So 5 options for each position. So number of 4-digit numbers with all odd digits = (5P1)^4 =5*5*5*5= 25*25=625
2. EVEN
there are 9 numbers to choose for three places without any restrictions. Total = 9 x 8 x 7 x 1 + 8 x 8 x 7 x 4 = 2296.
#riShu:-)
1. ODD
If we want that all 4 digits are odd,then the selection for all four places can be done from 1,3,5,7,9. So 5 options for each position. So number of 4-digit numbers with all odd digits = (5P1)^4 =5*5*5*5= 25*25=625
2. EVEN
there are 9 numbers to choose for three places without any restrictions. Total = 9 x 8 x 7 x 1 + 8 x 8 x 7 x 4 = 2296.
#riShu:-)
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