Question

What is the smallest number with 1,2,3,4,5 as factors

Answer 1

60.

Look at all the factors we want, and eliminate any that are redundant. We don't need the 2 because 2 is already a factor of 4, therefore any number with a factor of 4 also has 2 as a factor.

Now just multiply. 1*3*4*5 = 60