A bricklayer has 8 bricks. 7 of the bricks weigh the same amount and one is a little heavier than the others. If the bricklayer has one balance scale, how can they find the heaviest brick in ONLY two weighings? :)
2007-11-19 10:15:02 · 16 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
Take three of the bricks and weigh them against three of the others. If one side weighs more, the heavy brick is over there. If not, it's the one you didn't weigh.
Then, weigh two of the three bricks from the heavier group. If they're the same, it's the third. If they aren't, it's the heavier.
2007-11-19 10:21:55 · answer #1 · answered by JP 3 · 4⤊ 0⤋
We begin by weighing any 3 bricks with any 3 other bricks. There are two possibilities, either the scales will balance, or they will not balance.
Assume the scales balance. Then the heavier brick is one of the 2 bricks not weighed. Thus, in this case simply weigh each of these bricks against each other; the heavier brick will bring the scale down further.
Assumes the scales don't balance. Then we have narrowed down the heaviest brick to a set of 3 bricks. Thus place one brick of this set of three on one side of the scale, and place another on the other side. Either one will be heavier than the other, in which case we have found the heaviest brick, or the balance will be equal, in which case the heaviest brick was one of the three not weighed.
2007-11-19 12:10:35 · answer #2 · answered by Gir G 1 · 0⤊ 0⤋
Separate into three groups.
Group 1 has 3 bricks
Group 2 has 3 bricks
Group 3 hads 2 bricks
Balance Group 1 and 2
If they are equal then the heavier brick is in group 3, so balance each of the bricks in Group3 , to determine the heaviest.
If Groups 1 and 2 are not equal, take the heavier group and balance two of the three bricks. If they are equal, then the heaviest brick is the one you left out. If they are not equal, then the heavier one, is the odd one out.
2007-11-19 10:22:23 · answer #3 · answered by Jeƒƒ Lebowski 6 · 3⤊ 0⤋
First weighing: place any three bricks on one side of the scale, and another three on the other side. Note if one side is heavier than the other, or if the two sides are equal.
Second weighing: If the two sides were equal in the first weighing, take the two remaining unweighed bricks (one of which must be the heavier one) and place one on each side of the scale -- the heaviest one will be apparent.
If the first weighing showed unequal weights, take the heavier group of three bricks, put one brick from that group on one side of the scale, one more on the other side of the scale. If these two bricks are equal, the third unweighed brick is the heaviest. If one of the weighed bricks is heavier, it is the heaviest of all.
2007-11-19 10:43:24 · answer #4 · answered by Roger the Mole 7 · 1⤊ 0⤋
im not sure, but i think you take 6 on one side and 2 on the other, and see which side is heavier, and then see which section does not perfectly match the ratio 3:1. if the side with 2 is heavier then the 1 ratio, then put one brick one each side of the scale and choose the heavier one. if 6 is heavier do a 4 to 2 and see which scale is heavier than a 2:1. then weigh each brick in your hand.
Completely disregard this answer if you can only use the scales.
2007-11-19 10:27:55 · answer #5 · answered by Anonymous · 0⤊ 0⤋
First divide the bricks into two groups of three and one group of two. But the two groups of three on either side of the balance. If the groups weigh the same, then the other two bricks can be weighed against each ofther, and it would be obvious which one is heavier.
If one group of 3 is heavier than the other, then take any two of the bricks and weigh them against each other. If one is heavier than the other, then that is the heavy one. If they weigh the same, the one you left out is heavier.
Either way it's only two weighings.
2007-11-19 10:46:25 · answer #6 · answered by ǝɔnɐs ǝɯosǝʍɐ Lazarus'd- DEI 6 · 0⤊ 0⤋
Set one brick aside and on a balanced pan scale place 3 of the remaining six on one side.
If the scale is equal, the one left out is the heavier.
If not take the heavier 3 and do the same thing. Leave one out and balance the other two. If equal it will be the one left out, if not then the heaviest one.
2007-11-19 10:23:35 · answer #7 · answered by Franklin 5 · 1⤊ 0⤋
put three on each side of the balance scale, the other two stay on the ground. If the six that are on the scale balance, than one of the two left over will be the heavy one, weigh them to find it. If one set of three on the scale is heavier, then the heavy brick is one of those three. Take two of the three from this group and put them on opposite sides of the scale. If they balance, than the one you aren't weighing is the heavy one. If they aren't the same, then, you found the heavy one.
2007-11-19 10:24:25 · answer #8 · answered by circus011574 1 · 1⤊ 0⤋
put three bricks in each side of the balance.
if the balance, you know the heaviest must be one of the other 2, which you will get from the 2nd weighing.
if they don't balance, you know which set of 3 contains the heavier brick.
weigh any two of these bricks, if they balance the third is the heavier, if not it is obvious anyway.
2007-11-19 10:23:17 · answer #9 · answered by graham e 2 · 1⤊ 0⤋
put 3 bricks on each side of the scale
if they are even then it is one of the last two bricks- just weigh them which ever is heavier is the one.
If one of the original stack is heavier, the brick is in that stack. Weigh two of those bricks. If they are even then it is the brick you did not weigh. If one is heavier than the other then it is the heavier brick
2007-11-19 10:24:05 · answer #10 · answered by Walt C 3 · 1⤊ 0⤋