Let's do it this way.
80 is equal to 100% and we're trying to figure out what percentage would 40 be.
40 is half of 80. If you add 40 and 40 you'd get 80. So now that we know 40 is half of 80 we just need to figure out what percentage would be half of the whole (the whole is 100%)
So 100 split in half is 50.
So 40 would be 50% of 80.
I hope this helps :)
If you need anything else please message me.
