Answer:
There are 1500 different 4 digit numbers where the first digit is odd and the second digit is a multiple of 3
Explanation:
4 digit numbers are those with 4 digits e.g, 1000 is a 4 digit number,
Now, the first digit number has to be odd,
which gives us 1, 3, 5, 7, 9 so, 5 numbers.
The second digit has to be a multiple of 3, since the digits can range from 0 to 9, we have for the multiples,
3, 6, 9, so 3 numbers. (i.e. the 2nd digit can be either 3, or 6 , 9)
The last 2 digits can be any number from 0 to 9 i.e 10 numbers,
The total combination of these 4 digits is then,
(5)(3)(10)(10) = 1500 different 4 digit numbers