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nehs: Master | Next Rank: 500 Posts; Posts: 169; Joined: Tue Aug 24, 2010 2:15 pm; Thanked: 1 times

GMAT prep problems

by nehs » Wed Sep 22, 2010 5:09 pm

1.A certain list consists of several different integers. Is the product of al lthe integers positive?

1.Product of greatest and smallest integer in the list is positive
2.There are an even number of integers in the list

2. At a theatre, an adult ticket costs $5 and a child ticket costs $2. What is the mean(average) of all the adult and children tickets sold yesterday at the theatre?

1. The ratio of children tickets to adult tickets sold yesterday was 3 : 2
2. 80 adult tickets were sold yesterday

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Source: Beat The GMAT — Data Sufficiency | Wed Sep 22, 2010 5:09 pm

beatthegmatinsept: Master | Next Rank: 500 Posts; Posts: 422; Joined: Mon Aug 09, 2010 11:47 am; Thanked: 22 times; Followed by:1 members; GMAT Score:680

by beatthegmatinsept » Wed Sep 22, 2010 5:28 pm

nehs wrote:1.A certain list consists of several different integers. Is the product of al lthe integers positive?

1.Product of greatest and smallest integer in the list is positive
2.There are an even number of integers in the list

IMO C.

a) tells you that the smallest and greatest integers' product is positive. This could hold true in 2 scenarios:
both a and b are positive
or both a and b are negative.
If both are positive, then the product of all integers is positive
BUT, if both are negative, then the product of all integers will be positive depending on whether the number of integers in the list is even or odd.
(Odd number of negative integers will return a negative product)
So, Insufficient.

b) tells you nothing about the integers in the list being positive or negative.
Insufficient.

Together, b fills in the missing piece in a above. Hence, sufficient.

Being defeated is often only a temporary condition. Giving up is what makes it permanent.

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nehs: Master | Next Rank: 500 Posts; Posts: 169; Joined: Tue Aug 24, 2010 2:15 pm; Thanked: 1 times

by nehs » Wed Sep 22, 2010 5:36 pm

beatthegmatinsept wrote:
nehs wrote:1.A certain list consists of several different integers. Is the product of al lthe integers positive?

1.Product of greatest and smallest integer in the list is positive
2.There are an even number of integers in the list

IMO C.

a) tells you that the smallest and greatest integers' product is positive. This could hold true in 2 scenarios:
both a and b are positive
or both a and b are negative.
If both are positive, then the product of all integers is positive
BUT, if both are negative, then the product of all integers will be positive depending on whether the number of integers in the list is even or odd.
(Odd number of negative integers will return a negative product)
So, Insufficient.

b) tells you nothing about the integers in the list being positive or negative.
Insufficient.

Together, b fills in the missing piece in a above. Hence, sufficient.

That's right

However, I fail to understand how the information on greatest and smallest integers helps here. I thought we needed information to know if these integers are consecutive etc.

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beatthegmatinsept: Master | Next Rank: 500 Posts; Posts: 422; Joined: Mon Aug 09, 2010 11:47 am; Thanked: 22 times; Followed by:1 members; GMAT Score:680

by beatthegmatinsept » Wed Sep 22, 2010 5:39 pm

nehs wrote: That's right
However, I fail to understand how the information on greatest and smallest integers helps here. I thought we needed information to know if these integers are consecutive etc.

We don't care if they are consecutive or not.. All that we need to know is if they are positive or negative, and a gives you that.
Remember, its not asking you for Median or Mean here (where knowing more about the integers would be helpful).

Being defeated is often only a temporary condition. Giving up is what makes it permanent.

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nehs: Master | Next Rank: 500 Posts; Posts: 169; Joined: Tue Aug 24, 2010 2:15 pm; Thanked: 1 times

by nehs » Wed Sep 22, 2010 5:42 pm

beatthegmatinsept wrote: We don't care if they are consecutive or not.. All that we need to know is if they are positive or negative, and a gives you that.
Remember, its not asking you for Median or Mean here (where knowing more about the integers would be helpful).

Oh,yes - got it. Thanks again