How many positive 4-digit integers have only odd digits?
2 answers:
Answer:
Step-by-step explanation:
There are 5 possible odd digits to choose from: 1,3,5,7,9.
When we chose our first digit, we have 5 choices (the possible odd digits). For every one of those 5 choices, we can chose our second digit in 5 different ways again, then we have 5*5 = 25 ways for choosing our first two digits. We can do the same again, as for every one of the 25 first two digits, we can chose our third digit in 5 different ways (again, the odd numbers). So we multiply it by 5 again. Repeating this one more time, because we have 5 different ways to chose our fourth digit. At the end we will have
This is a commun counting technique.
You might be interested in
Answer: 8
Step-by-step explanation:
Given: Pedro cut a sheet of poster board into 10 equal parts.
let x be the total sheet.
then, one part of sheet= of the sheet
Now, His brother used some of the poster board and now 8/10 is left.
Therefore, if Pedro wants to make a sign from each remaining part of the poster board.
then, The number of signs he can make=
Hence, Pedro can make 8 signs.