Question

How many four-digit numbers ‘abcd’ exist such that a is odd, b is divisible by 3, c is even and d is prime?
A. 380
B. 360
C. 400
D. 520
E. 480

Answer 1

Hint: Take each digit separate and look for the values which satisfy the conditions.

Complete step-by-step answer:
Let us start with the values ‘abcd’ can take
‘a’ can take 5 values {1,3,5,7,9}
‘b’ can take 4 values {0,3,6,9}
‘c’ can take 5 values {0,2,4,6,8}
‘d’ can take 4 values {2,3,5,7}
Therefore, Total such 4 digit number =5×4×5×4= 400

Note: Similar problems including combination of conditions can be asked. In that case, the above method is best suited.