I came up with this all on my own without any help from any website, human or calculator...let me know if you think I'm wrong and tell me why I might be wrong.
They originally paid $10 each, but when the bell man brought back their money, they got back $5....So each person paid on average $8.4, so they got back on average $1.6. 1.6x3 equal's $4.8. They gave the bell man 2 dollars (4.8-2=2.
. So now you have the hotel's money (25) + the bell man's money (2) + the men's money (2.
= $29.8, which you would round up to $30 since you had to round 8.333333 up to 8.4 (.07 ((the rounded up amount approx))x3 ((the amount of men)) = .21 which is the amount missing from the $29.8 once you cancel out the taken away from and added on amounts for both rounded numbers).
Here's it laid out in mathimatical equation's:
10x3=30 (original payment)
30-5=25 (payment hotel kept)
25/3=8.4 (What each person paid...rounded)
10-8.4=1.6 (What each person got back...figured from rounded number)
1.6x3=4.8 (What all three got back when figuring with rounded numbers)
4.8-2=2.8 (total amount got back minus the bellboy's tip)
25+2+2.8=29.8 (Hotel payment plus the bellboy's tip plus the rounded amount they have left)
We rounded the 8.3333 (infinity) up to 8.4, so you get the .07 back
.07x3=.21 (amount the each person got back on top of the 1.6 times all three of the men)
25+2+2.8+.21=30.01 (Hotel payment plus the bellboy's tip plus the rounded amount they have left plus the round amount they got back on top of the 1.6)
Now the 2.8 was figured from a rounded up number, so it isn't exact 2.8 and the .07 isn't exactly .07, so when the taken away and added on total for each rounded number are cancelled out, they make an even $3.
I figured this out all on my own. I did not look up anything or use a calculator anywhere, I sat here for about 5-10 minutes figuring out the answer and I got it. And I am not lying, I actually didn't have any help figuring this out.