UMAT Question Thread!

[planningsaw]

Hi can someone help me with this umat question! Answer is D!

[grindr]

Could someone please attempt this question?

You have eight marbles that weigh 20 grams each, and one marble that weighs 30 grams. You are unable to determine which is the heavier marble by looking at them. You have a weighing scale that consists of two pans. You want to determine which marble is the heaviest using this scale.
Question 16
What is the minimum number of weighings required to be certain to know which is the heavier marble?
A. One
B. Two
C. Three
D. Four

The answer is B, but I think A is possible.

Does anyone find that the medentry drill answers are debatable?

[natdogg]

Could someone please attempt this question?

You have eight marbles that weigh 20 grams each, and one marble that weighs 30 grams. You are unable to determine which is the heavier marble by looking at them. You have a weighing scale that consists of two pans. You want to determine which marble is the heaviest using this scale.
Question 16
What is the minimum number of weighings required to be certain to know which is the heavier marble?
A. One
B. Two
C. Three
D. Four

The answer is B, but I think A is possible.

Does anyone find that the medentry drill answers are debatable?

I think the problem lies within the wording of the question. While it is technically POSSIBLE to determine which of the marbles is heavier through only one weighing, you cannot be CERTAIN that the 4 marbles you put on each pan are of equal weight. If the heavier marble snuck into one of those pans, then what?
So I think B is the only possible answer

[grindr]

I mean that, just say you weighed 4 marbles in each pan (one marble is not included) If one of the sides had the heavier marble than you would weigh those marbles again somehow so you would have more than 1 weighing.

But if when you weighed it, the scale was equal, then you would know that the marble you excluded would be the heavier one...
So one weighing???

[natdogg]

I get what you're saying, but the question asks for the minimum number of weighings required to be CERTAIN which marble is the heavier one. So if you split it into 4 per pan, only one of the possible paths requires one weighing, the other pathway requires 3 weighings, so you can only be CERTAIN which marble is heavier after 3 weighings.
If the 4 marbles in each of the two pans aren't of equal weight, then you can't be certain which marble is heavier after just one weighing, right?

So like, from one action: placing 4 marbles in each pan, you get two possible outcomes. The scales balance, or they don't. If they balance, you've worked it out in one weighing, if they don't balance, you need to do 3 weighings.
But the idea is that from just this one action, you cannot be 100% certain the scales will balance, so you cannot be 100% certain that it will only take one weighing to find the heavier marble.
Does this kinda make sense?

[grindr]

I understand what you're saying and I don't like this question.
Thank you though 

[Mattjbr2]

Do Section 3 Pick the Middle Rotational questions ever involve shapes moving around 3 sided figures such as triangles? Or are 4 sided figures (e.g. squares) the most basic shapes used? From the questions that I've done thus far, I've yet to see a 3 sided configuration. Am I wasting my time in mapping out all possible patterns around a triangle?

[cookiedream]

Do Section 3 Pick the Middle Rotational questions ever involve shapes moving around 3 sided figures such as triangles? Or are 4 sided figures (e.g. squares) the most basic shapes used? From the questions that I've done thus far, I've yet to see a 3 sided configuration. Am I wasting my time in mapping out all possible patterns around a triangle?

You can never really predict what will/will not come up on the real exam. In the practice I did last year, I've seen a few triangles used, but most of them were in conjunction with another shape. For example, the triangle was beside another triangle or the triangle was inside a larger square. I mapped out these kind of movements for triangles, squares, pentagons and hexagons - which are the most common shapes that come up in pick the middle-type questions.