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)

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!


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