There are three envelopes and exactly two statements are written on each of the envelopes. The statements on one of the envelopes are BOTH TRUE, the statements on the other envelope are BOTH FALSE and the remaining envelope has ONE TRUE and ONE FALSE statement. Here is what is written on the three envelopes:

First Envelope:
(a)The formula is not in here.
(b)The formula is in Envelope 2.

Second Envelope:
(a)The formula is not in Envelope 1.
(b)The formula is in Envelope 3.

Third Envelope:
(a)The formula is not in here.
(b)The formula is in Envelope 1.

Which envelope contains the formula ?

If it was in Envelope 1 then both envelopes 1 and 2 would have two lying statements.

If it was in Envelope 2 then envelopes 2 and 3 would both have one true and one false statement.

If it was in Envelope 3 then the first envelope has one true and one false, the second envelope has two true statements and the third has two false statements.

Therefore, envelope 3 contains the formula.

Posted by Lewis on 2003-07-25 22:26:41