Question

How many 5 digit numbers have atleast one even digit ?
options:
a)86875
b)88775
c)85625
d)87895

Answer 1

Answer: 86,875

Assuming that no leading zeros are allowed, the numbers range from 10,000 to 99,999. Counting both endpoints, that's 90,000 integers.

There are 5 odd digits: {1, 3, 5, 7, 9}. There are therefore 55=312555=3125 integers from 10,000 to 99,999 that contain all odd digits.

Now, to get the integers that contain a least one even digit, a simple subtraction is required: 90,000 - 3,125 = 86,875