Find the number of even positive numbers which have four digits.

Explanation

A number of even if the digit at its units place is one out of 0,2,4,6,8.
Number of ways of filling units place =5
Number of ways of filling ten's place=10
Number of ways of fillig hundred's place =10
Number of ways of filling thousand's place =9 `" `"(0 cannot be put at thousand's place)
`therefore ` By the fundamental principle of multiplication , total number or ways is `=5xx10xx10xx9=4500`