a = 2 4 6 8
b = 0 5
c = 2, 3, 5, 7
d = 1, 3, 5, 7
4 choices for a
2 choices for b
4 choices for c
4 choices for d
Mulitply to find how many 4 digit numbers exist under these conditions.
How many four-digit numbers abcd exist such that a is even, b is divisible by 5, c is prime, and d is odd?
4 answers
there are 4 even digits
only 1 digit, 5 , is divisible by 5
(although you could make an argument for 0)
1, 3, 5 , 7 or four digits are prime
1,3,5,7,9 or 5 digits are odd
so 4*1*4*5 = 80
only 1 digit, 5 , is divisible by 5
(although you could make an argument for 0)
1, 3, 5 , 7 or four digits are prime
1,3,5,7,9 or 5 digits are odd
so 4*1*4*5 = 80
I agree with Damon, I was thinking about zero and in 10 , 20 , etc.
I got 80 to thanks Damon and Dr Jane