[SamAdams76]

I don't understand why it's necessary to multiply odd numbers by three before adding the one to make it even.

By simply adding a one every time you divide by half to get an odd number, you will get down to the number 1 all the faster.

[LibWhacker]

I don't understand why it's necessary to multiply odd numbers by three before adding the one to make it even.

I can only speculate that Collatz himself knew it was true, or proved it was true, in that case.

But when he looked at multiplying by three, he couldn't prove it.