Another couple of nice easy puzzles

You've got 10 machines that each produce bags of flour. They're all supposed to produce bags weighing exactly 1kg. However one machine is faulty and produces bags with 10% more flour than the others. By making one weighing of bags produced by the machines, how can you determine which machine is faulty?


OK, a similar problem now.

You have nine coins that look identical. 8 of them are of identical weight but one is ever so slightly heavier. You have a set of balances and by making no more than two weighing with the balances, how do you determine which is the heavy coin?

 

Monty Python sketches? How so?

 

Nope, I think it's almost as boring as Basketball.

 

I solved the problem with 9 coins but not the one for 10 bags of flower
here is my answer:





First Weighing
Put three coins on one side of the scale and three coins on the other side. Leaving three coins not getting weighed.

This weighing can then result in two possibilities:

Possibility One: The scale is balanced
Therefore the 6 coins that were weighed are all equal in weight.
This means of the 3 coins not weighed one of them is the heavier coin.

Possibility Two: The scale is not balanced
The heavier coin is one of the 3 coins on the heavier side of the scale

Both these possibilities will leave a group of 3 coins with the heavier coin in that group.

Second Weighing
Place one coin aside. Weigh the other two coins.

Possibility One: The scale is balanced
Therefore the heavier coin is the coin not on the scale.

Possibility Two: The scale is not balanced
Therefore the heavier coin is the heaveir coin on the scale


Im thinking the flour one has something to do with the fact that the heavier bag is 10% more and we have 10 machines hmmmm

Question for Sax_Machine can the machines produce multiples bags that we can then weigh? Example so we could weigh 50 bags from one machine and 20 from another.

btw yes i love puzzles like these

 

Yes. I think you've cracked this one, so let me give you another in the mean time.

Ok, there is an empty room with an electric light in the middle. Outside the room you have three light switches. One switch operates the lightbulb, the other two are not connected to anything. It is not possible to tell whether or not the light is on from outside of the room. It is not possible to remove the light from the room. You may go into the room once. How do you determine which switch operates the light-bulb?

 

u didnt answer my previous question


also question for this one are the light switches labelled on and off
and does the lightbulb start turned off inside the room

 

i want to know now

but im going to be mad if its something gay like while in the room get ur friend to start turning on and off the light switches

 

Yes I did. What was the first thing I said in my post?

I think you'll find it was "YES".

Well I'll tell you the solution to the lightswitches one since no-one else cares about these puzzles so probably won't shoot me for giving the answer so soon.

Turn one switch to the on position and leave it for a good ten minutes or so.

Turn it off and turn on the second switch.

Go into the room.

If the light is on then it's the second switch. If the light is off, then touch the bulb. If it's warm then it's the first switch, and if it's not warm then it is neither the first nor the second switch so it must be the third switch.

 

yer youd get one bag from the firs tmachine, two form tehs econd, three, etc


then youd take away the amount of weight that would assume all bage are equal and see how many kg are left. that will correspond with the faulty machine.

 

yes, although it would be how many 100gs are left.

 

i thought the bags were 10kg, caus of all the other '10's in teh question.

 

grr that lightbulb one was lame