Brain Teasers
Drash and Rabb
On the Planet Necro there are two types of metals. One is Drash which weighs 127 Necrograms, and Rabb which weighs 50 Necrograms. You have as much play-doh, Drash, and Rabb as you need. You have a balance scale and you need to make a ball of play-doh equal to 304 Necrograms. How?
Answer
Put the Rabb on the scales. Put play-doh on the opposite side so it balances the Rabb. Then divide the play-doh in half so that each half balances the other. Now you have a 25 Necrogram ball of play-doh. Now put the Drash on the scales and enough play-doh to balance it, then mix the 127 and 25 Necrogram balls of play-doh together. That makes 152 Necrograms. Put that ball on the scales and enough play-doh to balance that. Combine these and you will have a 304 Necrogram ball of play-doh.Hide Answer Show Answer
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Comments
Your solution is much harder than need be. Why not put all the Drash on the scale and enough Play-doh to balance. Then take this Play-doh (127 necrograms) plus the Drash (127 necrograms) plus the Rabb (50 necrograms)and put them all on one side of the scale to give you 304 necrograms Then simply balance with Play-doh.
He's right...
Good idea, but you didn't say how much of each kind of metal yielded the masses you gave. Was it a pound or a ton? Since you said that we have all of either kind of metal that we want, there's not enough info to support the inference that whatever amount of metal you put on the scale will magically weigh the exact mass that you have given.
When I said "pound or ton" I meant does 50 necrograms of Rabb fill a shoebox or a dump truck, with all the metal you want and only a balance scale, you would have no way of knowing.
Seaman, you're apparently missing something. It's a BALANCE scale. If you know the weight of one Drash, for example, then you can put enough play doh to exactly balance that drash on the scale. You will then know the exace weight of the play doh. There is nothing logically wrong with this teaser.
The part that I felt is slightly illogical is saying that a metal weighs so many necrograms. Its weight would obviously depend on the quantity of metal used. So I guess I answered two units of Drash and one unit of Rabb to balance the play-doh.
I figured it like Krishnan did, but after reading the answer, I think the intention is that there are only the two quantities of metal available, each of the given masses. There (apparently) are no multiples of either the drash or rabb to use. It's as if you have only two weights to use in addition to any playdoh you wish.
Yeah, poorly phrased teaser and very easy regardless. I don't know why it has such a high difficulty rating.
Ditto of Awkward. The problem would read much better if the "types of metal" part was skipped and replaced with two weights of 50 and 127.
Ridiculously easy even with the poor set up.
Ridiculously easy even with the poor set up.
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