Question: Jets Fans in a Dormitory

Comment on Jets Fans in a Dormitory

How you got the 5/12 ?
greenlight-admin's picture

If we've accounted for 5/12 of the students, then 7/12 of the students are unaccounted for.

Likewise, if 2/5 of a population are female, then we can conclude that 3/5 of the population are male.

I made the mistake of multiplying the fractions 1/3, 1/6 and 1/12 instead of adding them since I read the "of". When should I add instead of multiplying?
greenlight-admin's picture

This is still a multiplying situation, except we don't really need to write it as such.

For example, we can take "1/3 of the students are Jets fans" and write: (1/3)T = # of Jets fans (where T = TOTAL number of students)

Likewise, we can take "1/6 of the students are Bears fans" and write: (1/6)T = # of Bears fans

And (1/12)T = # of Dolphins fans

So, the number of fans accounted for = (1/3)T + (1/6)T + (1/12)T
= (7/12)T

And so on...

Does that help?

I converted the fractions to decimals/percentages, summed them up and had a different result:

1/3 --> 33.33%
1/6 --> 16.66%
1/12--> 0.08%

For a total of approx 51% of Jets', Bears' an Raiders'fans. The rest (49%) is 30 Dolphins' fans, which, adding up, is closer to a total of 60 than 72.

Therefore, choice A (60) was more approximate to be the correct answer. Where did I go wrong here?
greenlight-admin's picture

Great approach!

The only problem is here: 1/12--> 0.08%

1/12 ≈ 0.08 ≈ 8% (not 0.08%)

Cheers,
Brent

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