Monthly Brain Teaser and Decembers AnswerTuesday, January 10th, 2012
For Christmas you were given this problem:
A baron builds a castle on a square island and surrounds the island with a moat that in turn forms a square. The moat is 10 metres wide. An enemy decides to attack the castle by crossing the moat on long strengthened planks. Unfortunately when they arrive they find that the planks are half a metre too short. Is there some way they can still get across the moat and onto the island or must they return home in disgrace?
The answer? The enemy placed a plank across a corner of the moat, and then placed a plank from that onto the other side of the moat. The planks thus looked like an inverted T. Enemy troops were then able to cross the moat and attack the castle.
Now try this one:
The managing director rang the payroll department and told the trainee who answered the phone that he needed by lunchtime without fail the average salary of the ten people who made up the management group. He rang off before she was able to tell him that the whole department was out on a training course, that she was the only one in the department that day, and that she did not have access to senior staff salaries. Nevertheless she knew that all the managers were at a meeting and at this moment should be on their coffee break. So she went to their meeting room and asked if they would please give her their individual salaries so that she could do the calculation. They made clear that in no way would they tell her, a young trainee, their salaries, and neither would they write them down anywhere in case the paperwork went astray and any of their colleagues discovered that one or two of them were paid much more than the rest. The trainee was, however, a resourceful young lady and, after a few moments thought, suggested to them a way by which she could get the information she needed without anyone having to write down his or her salary. The managers were perfectly happy with this and she got what she wanted before they resumed their meeting. What did she do?