Brain Teasers
Diamond Theft
There is a famous diamond displayed in a room that measures 15 meters by 15 meters by 15 meters. The room is made entirely of concrete blocks and the floor is covered with a thick carpet. The only thing in the room is the diamond that is housed under a glass cube. The glass cube stands on a one-meter pedestal in the centre of the room. Alarm wires spaced eight centimetres apart and running parallel to each other lie under the carpet. The alarm will trigger if more than four kilograms of pressure is applied to any individual wire. Will Carlo who weighs 74 kilograms was able to steal the famous diamond using the following equipment: a five meter 2 x 4 board, four leather straps (each two meters long and five cm wide), a hammer, and a saw. How could he do it without triggering the alarm?
Answer
Will Carlo stole the diamond in the following manner: First, he cut five meter 2 x 4 boards in half. Then using the available straps, he fastened the two boards to his feet like skies. With the boards strapped to his feet, his weight was displacing enough so that he did not exceed the wire's weight tolerance and triggers the alarm. Carlo then slowly and carefully walked to the centre of the room, smashed the glass cube with the hammer, took the diamond and returned the same way he came in.Hide Answer Show Answer
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You didn't really show your workings, and I only half looked at it, but I'm fairly sure that when he lifts one foot up to walk forward that he will exceed the weight restriction.
Well technically speaking if a board is 2.5 meters long (250 cm) then it will be distributing the weight over 31 wires at any given instant. (250cm / 8cm = 31 and some change. 31 wires can handle roughly 248kg @ 8kg each, without tripping the alarm. The only problem with this is the physics of the flexibility of the board. You would have to have a stronger material than a 2x4 to evenly distribute the weight along the length of 2.5m because I can assure you with the flexibility inherent in wood. More than 8kg of preasure would on a wire directly under the feet and would lighten up as the you moved along the board away from the foot. So this solution would not work in the real world. I suggest this criminal find another line of work. --RAYN
he could do that without saw and hammer. To use again ski-related solution, he could have bound his legs horisontally on board , like snowboard, and could slide whole board toward center - move left side to 45 degrees, then right up by moving right side. In that way, his weight would be even better spread (in best case to 5m, in worst case to 3.5m, as compared to previous 2.5m )
Did the weight of such a large diamond not add to his weight when leaving and trigger the alarms?
Would the owner have also put an alarm on the glass cube so that when it was broken, the alarm would have gone off? Also, if it were my diamond, I would put an alarm on the pedestal so that if there wasn't enough weight on the pedestal (the weight of the diamond and the glass cube) that another alarm would go off.
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