Maths using Double type

Can anyone explain why relatively simple maths do not work in my sub when I have a variable declared as a type of Double?
I have one declared as integer set as 3 and one declared as double set to 0.6.
When I check if 3 * 0.2 = 0.6 I get a false... See sample sub below.

Sub testIt()
Dim FirstNumber As Double, SecondNumber As Integer
FirstNumber = 0.6
SecondNumber = 3
If (SecondNumber * 0.2) = FirstNumber Then
    MsgBox "Worked"
Else
    MsgBox "Not Worked >" & (SecondNumber * 0.2) & "<>" & FirstNumber & "<"
End If

End Sub

Confused....