Posts: 1585
Threads: 8
Joined: November 27, 2018
Reputation:
6
Scales question. What is the answer?
December 1, 2018 at 12:13 am
Let's see who gets it first. Please no cheating. 
You have 8 balls that look identical, but one in the group is slightly heavier than the others. You also have a single balance scale to find the heavier ball. What is the least amount of times you would have to use the scale to consistently identify the heavier ball? What method would you use to find that ball each time?
First one to get it wins a stuffed rainbow unicorn.
Posts: 232
Threads: 2
Joined: November 29, 2018
Reputation:
0
RE: Scales question. What is the answer?
December 1, 2018 at 12:16 am
(This post was last modified: December 1, 2018 at 12:18 am by Cherub786.)
(December 1, 2018 at 12:13 am)T0 Th3 M4X Wrote: Let's see who gets it first. Please no cheating.
You have 8 balls that look identical, but one in the group is slightly heavier than the others. You also have a single balance scale to find the heavier ball. What is the least amount of times you would have to use the scale to consistently identify the heavier ball? What method would you use to find that ball each time?
First one to get it wins a stuffed rainbow unicorn.
Is the weight of the other 7 balls identical?
If so, you would potentially only have to use the scale 1 time to identify the heavier ball
Posts: 15351
Threads: 118
Joined: January 13, 2014
Reputation:
116
RE: Scales question. What is the answer?
December 1, 2018 at 12:18 am
3.
Put four on each side of the scale. You've reduced the candidates to 4.
Put two on each side of the scale. You've reduced the candidates to 2.
Put one on each side of the scale. You've found the ball.
"There remain four irreducible objections to religious faith: that it wholly misrepresents the origins of man and the cosmos, that because of this original error it manages to combine the maximum servility with the maximum of solipsism, that it is both the result and the cause of dangerous sexual repression, and that it is ultimately grounded on wish-thinking." ~Christopher Hitchens, god is not Great
PM me your email address to join the Slack chat! I'll give you a taco(or five) if you join! --->There's an app and everything!<---
Posts: 1585
Threads: 8
Joined: November 27, 2018
Reputation:
6
RE: Scales question. What is the answer?
December 1, 2018 at 12:21 am
(December 1, 2018 at 12:16 am)Cherub786 Wrote: (December 1, 2018 at 12:13 am)T0 Th3 M4X Wrote: Let's see who gets it first. Please no cheating.
You have 8 balls that look identical, but one in the group is slightly heavier than the others. You also have a single balance scale to find the heavier ball. What is the least amount of times you would have to use the scale to consistently identify the heavier ball? What method would you use to find that ball each time?
First one to get it wins a stuffed rainbow unicorn.
Is the weight of the other 7 balls identical?
If so, you would potentially only have to use the scale 1 time to identify the heavier ball
Yes, 7 identical and 1 heavier but looks the same.
Posts: 232
Threads: 2
Joined: November 29, 2018
Reputation:
0
RE: Scales question. What is the answer?
December 1, 2018 at 12:24 am
(This post was last modified: December 1, 2018 at 12:26 am by Cherub786.)
(December 1, 2018 at 12:21 am)T0 Th3 M4X Wrote: (December 1, 2018 at 12:16 am)Cherub786 Wrote: Is the weight of the other 7 balls identical?
If so, you would potentially only have to use the scale 1 time to identify the heavier ball
Yes, 7 identical and 1 heavier but looks the same.
Okay then Steel's answer is correct.
But there is a possibility you can identify the heavier ball by using the scale only once if you happen to pick the heavier ball the first time and weigh it against one of the 7.
Potentially the answer is once
So it is possible to identify the heavier ball with a single weighing, though the probability is 1/4 (25% chance)
Posts: 1585
Threads: 8
Joined: November 27, 2018
Reputation:
6
RE: Scales question. What is the answer?
December 1, 2018 at 12:27 am
(December 1, 2018 at 12:24 am)Cherub786 Wrote: (December 1, 2018 at 12:21 am)T0 Th3 M4X Wrote: Yes, 7 identical and 1 heavier but looks the same.
Okay then Steel's answer is correct.
But there is a possibility you can identify the heavier ball by using the scale only once if you happen to pick the heavier ball the first time and weigh it against one of the 7.
Potentially the answer is once
So it is possible to identify the heavier ball with a single weighing, though the probability is 1/8
Right, but you have to be able to use the method consistently, as per the question. There are actually two ways to solve the problem, but they both equal 3 tries.
Posts: 20476
Threads: 447
Joined: June 16, 2014
Reputation:
110
RE: Scales question. What is the answer?
December 1, 2018 at 12:29 am
(This post was last modified: December 1, 2018 at 12:30 am by ignoramus.)
I don't think it's 25%
You still only have a 1 in 7 chance of picking the heavier ball in the first place.
No God, No fear.
Know God, Know fear.
Posts: 232
Threads: 2
Joined: November 29, 2018
Reputation:
0
RE: Scales question. What is the answer?
December 1, 2018 at 12:35 am
(December 1, 2018 at 12:29 am)ignoramus Wrote: I don't think it's 25%
You still only have a 1 in 7 chance of picking the heavier ball in the first place.
No, you pick 2 balls at a time, so the probability is increased to 25%
Posts: 15351
Threads: 118
Joined: January 13, 2014
Reputation:
116
RE: Scales question. What is the answer?
December 1, 2018 at 12:36 am
(December 1, 2018 at 12:29 am)ignoramus Wrote: I don't think it's 25%
You still only have a 1 in 7 chance of picking the heavier ball in the first place.
2 in 8 is 25%.
"There remain four irreducible objections to religious faith: that it wholly misrepresents the origins of man and the cosmos, that because of this original error it manages to combine the maximum servility with the maximum of solipsism, that it is both the result and the cause of dangerous sexual repression, and that it is ultimately grounded on wish-thinking." ~Christopher Hitchens, god is not Great
PM me your email address to join the Slack chat! I'll give you a taco(or five) if you join! --->There's an app and everything!<---
Posts: 1585
Threads: 8
Joined: November 27, 2018
Reputation:
6
RE: Scales question. What is the answer?
December 1, 2018 at 12:36 am
(December 1, 2018 at 12:29 am)ignoramus Wrote: I don't think it's 25%
You still only have a 1 in 7 chance of picking the heavier ball in the first place.
You can get lucky and get the ball with one try, but you can't consistently use that method and get it in one try.
|
