Question

This a question from a textbook called "How to think like a mathematician".

Suppose that three friends have a meal for $25. They misread the bill, thinking it says $27, give the waiter $10 each and ask for a total of $3 in change, i.e. $2 less than they should get. The waiter puts $25 in the till, gives each of the friends $1 and secretly pockets the extra $2.
Later the waiter does some calculations. The friends paid $(10 − 1) = $9 each which is $27 and he kept $2, giving a total of $29. But the friends gave $30. What happened to the extra $1? This a question from a textbook called "How to think like a mathematician".

Suppose that three friends have a meal for $25. They misread the bill, thinking it says $27, give the waiter $10 each and ask for a total of $3 in change, i.e. $2 less than they should get. The waiter puts $25 in the till, gives each of the friends $1 and secretly pockets the extra $2.
Later the waiter does some calculations. The friends paid $(10 − 1) = $9 each which is $27 and he kept $2, giving a total of $29. But the friends gave $30. What happened to the extra $1? @Mathematics

Answer 1

Bill = $ 25
Returned = $ 3 ( $ 1 each)
Waiter Kept = $ 2
so, total is $ 30

Answer 2

what u r doin u are adding $ 27 and $ 2.

Answer 3

Thanks. I thought that was all but sometimes when it's something so simple you doubt yourself.