Trick Question From School Teacher

[vesuvius123]

3 people pay £10 each to a waiter for a £30 bill the waiter then realises she has charged £5 too much but cant work out how much to give each back so just gives each £1 and pockets the other £2, so each person has paid £9 each which adds up to £27 plus her £2 is £29 what has happened to the other £1.

[bert_h]

Ha, ha. 3 times £9 = £27 = £25 for the meal and £2 for the waitress. You can't make any sense of adding the waitress's £2 to the diners' payment of £27, because her £2 was already part of that £27.

[plowter]

The trick is in the wording of the question 'plus her £2'.
As bert says, it shouldn't be added to the £27.

Look at the facts another way.
1. The diners paid £30, the cost was £25.
2. Difference is £5.
3. That £5 is made up the returned £3 plus the £2 profit for the waitress.

[Gizmonster]

.... just thought I'd add my two penneth, even though the above answers explain it fully:
There is no missing pound, it dosn't make sense to add the £2 on to the £27 to make £29. If anything, you need to subtract the £2 to get back to the £25 bill. The diners have all paid £9 each, making £27 in total. This £27 comprises the £25 bill and the £2 tip for the waiter.

[factor-fiction]

Maths teachers used to try that one on us when we started grammar school forty odd years ago. Despite massive inflation the figures haven't changed, although in those days the problem was often expressed in dollars