Easier again:

Make 24 using only the digits 1, 4, 5 and 6, with the following conditions:

* They should not be clubbed /joined (to form such as 64 or 51 etc.)
* Only the basic arithmetic operations (+, -, \* and /) are allowed to be performed. (Means - No use of powers / roots / factorials etc.)
* All the given digits should be used and
* All the given digits should be used only once