Question: Precious Metals

Comment on Precious Metals

On the question about 8 countries that produced rhenium. Couldn't there have been just 7 due to rounding? For example, if Country 1 had produced 30.4%, Country 2 20.4, 3 20.3, 4 15.4, 5 8.4, 6 4.4 and 7 2.4. That adds up to more than 100% with just 7 countries. There are lots of ways the data could match the set and only have 7 countries producing.
gmat-admin's picture

Your counter-example assumes that the data values are rounded to the nearest integer. However, there is nothing in the question that confirms this assumption.

So, we must assume that the given percentages are exact values. So, for example, Country B produced 30% of the Rhenium (and not 30.4% as you suggest)

Hello,
for the second statement how we concluded that total production of Country B&C will be 150 since when they doubled production we can consider only doubled amount not the sum of doubled+normal production.
gmat-admin's picture

Sorry for the confusion. We aren't saying that the total production from countries B and C is 150; we're saying that the NEW total for ALL of the counties (after B and C doubled their production) is 150 units.

We started by seeing what would happen if the original total volume of Rhenium is 100 units.

So, we can calculate the production of each country:
Country A: 4 units
Country B: 30 units
Country C: 20 units
Country D: 15 units
Country E: 8 units
Country F: 2 units
All other countries: 21 units
TOTAL = 100 units

If countries B and C DOUBLED their production, we get:
Country A: 4 units
Country B: 60 units
Country C: 40 units
Country D: 15 units
Country E: 8 units
Country F: 2 units
All other countries: 21 units

As we can see, the NEW production total = 150 units

Of these 150 units, Country D produced 15 units (i.e., 10% of the NEW production total.

Thank you Brent,
What I do not understand is that sum of all volume altogether is 79 before doubling the production and after doubled it is 119, Now I am confusing how it happens to be 100 and 150 when D=15 units. I mean when we consider D=15 then how we can calculate other countries more units than they are.

gmat-admin's picture

Sorry, I forgot to add in the row representing all OTHER countries (who produce the remaining 21% of rhenium).

I've edited my response above.

Therefore by the current credit of each country and even after B&C doubled the answer to the middle item is NO? Am I right
gmat-admin's picture

The answer to the middle question is YES.

If countries B and C had DOUBLED their production, the NEW production total = 150 units (see my calculations above)

Country D produced 15 of those 150 (hypothetical) units, which means country D produced 10% of the total.

Thanks a lot for the very prompt reply.

for a) can you just check that the missing country must have 100%-92% production = 8% production.

so that 17% + 6% + 8% is less than 50%+ required to answer the question?
gmat-admin's picture

That is perfectly sound reasoning - nice work!

Cheers,
Brent

Hi Brent!
Can you kindly re-explain the first statement (a)?
I fully understand statements (b)and (c), but I couldn't understand statement (a).

Thank you very much!
gmat-admin's picture

Hi Lina,

Here's a different way to explain why statement (a) isn't true:

The main issue here is that the chart only refers to 6 of the world's countries.

We know that countries F and B are the 1st and 3rd leading countries when it comes to osmium production, but we don't know anything about the country that's 2nd in osmium production. I'll refer to this 2nd country as the MISSING country.

When it comes to bismuth production, countries F and B combined account for 23% of production. So, the only way for the top 3 osmium producers to produce over half of the world's bismuth would be for the MISSING country to produce at least 27% of the world's bismuth. This, however, is impossible because the chart already accounts for 92% of the world's bismuth production. So, even if the MISSING country produced the remaining 8% of bismuth, the top 3 osmium producers still wouldn't produce more than half of the world's bismuth.

Does that help?

Perfect, all clear. Thank you Brent!

Hi Brent, to clarify for statement 2, my understing is initial total of B and C is 30 & 20. So total is 50. After doubled is 60 & 40. So total is 100. Therefore the new total value now is 50 + 100 = 150. Is my understanding correct?
gmat-admin's picture

That's correct.

Thanks Brent for confirmation.
As confused with a post above stating that the NEW total for ALL of the counties (after B and C doubled their production) is 150 units.

Hi Brent, for C, how could we assume that the total column sum is 100% in order to calculate whethere there's 8 countries or not since it's not being given in the statement? In fact 100% is being assumed in a too?
gmat-admin's picture

Yes we have to assume that the ENTIRE world's production of rhenium accounts for 100% of the rhenium production.

The main idea here is that there must be more than six countries producing rhenium. We know this because the six countries listed here account for only 79% of the world's production.
So some additional countries must account for the remaining 21% of the world's production.

For example, if I have a bunch of apples, and I give you 79% of them, then I must have kept the remaining 21% of the apples for myself.

Does that help?

Get it thanks Brent.

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