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A certain club has 20 members. What is the ratio of the member of 5-member

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A certain club has 20 members. What is the ratio of the member of 5-member

by BTGModeratorVI » Tue Mar 10, 2020 7:14 am

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A certain club has 20 members. What is the ratio of the member of 5-member committees that can be formed from the members of the club to the number of 4-member committees that can be formed from the members of the club?

A. 16 to 1
B. 15 to 1
C. 16 to 5
D. 15 to 6
E. 5 to 4

Answer: C
Source: GMATPrep test
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Re: A certain club has 20 members. What is the ratio of the member of 5-member

by Jay@ManhattanReview » Thu Mar 12, 2020 12:33 am
BTGModeratorVI wrote: ↑
Tue Mar 10, 2020 7:14 am
 A certain club has 20 members. What is the ratio of the member of 5-member committees that can be formed from the members of the club to the number of 4-member committees that can be formed from the members of the club?

A. 16 to 1
B. 15 to 1
C. 16 to 5
D. 15 to 6
E. 5 to 4

Answer: C
Source: GMATPrep test
Ratio of the member of 5-member committees to the number of 4-member committees

= 20C5 / 20C4 = [(20.19.18.17.16)/(1.2.3.4.5) / (20.19.18.17)/(1.2.3.4)] = 16/5

The correct answer: C

Hope this helps!

-Jay
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Re: A certain club has 20 members. What is the ratio of the member of 5-member

by Scott@TargetTestPrep » Thu Mar 12, 2020 6:36 am
BTGModeratorVI wrote: ↑
Tue Mar 10, 2020 7:14 am
 A certain club has 20 members. What is the ratio of the member of 5-member committees that can be formed from the members of the club to the number of 4-member committees that can be formed from the members of the club?

A. 16 to 1
B. 15 to 1
C. 16 to 5
D. 15 to 6
E. 5 to 4

Answer: C
Source: GMATPrep test
The ratio is the following:

(20C5) / (20C4) = [(20 x 19 x 18 x 17 x 16) / 5!] / [(20 x 19 x 18 x 17) / 4!]

= [(20 x 19 x 18 x 17 x 16) / 5!] x [4! / (20 x 19 x 18 x 17)]

= 16/5

Answer: C

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Re: A certain club has 20 members. What is the ratio of the member of 5-member

by Brent@GMATPrepNow » Thu Mar 12, 2020 7:05 am
BTGModeratorVI wrote: ↑
Tue Mar 10, 2020 7:14 am
 A certain club has 20 members. What is the ratio of the member of 5-member committees that can be formed from the members of the club to the number of 4-member committees that can be formed from the members of the club?

A. 16 to 1
B. 15 to 1
C. 16 to 5
D. 15 to 6
E. 5 to 4

Answer: C
Source: GMATPrep test
5-member committees
Since the order in which we select the committee members does not matter, we can use COMBINATIONS
We can select 5 people from 20 people in 20C5 ways
20C5 = (20)(19)(18)(17)(16)/(5)(4)(3)(2)(1)

4-member committees
Since the order in which we select the committee members does not matter, we can use COMBINATIONS
We can select 4 people from 20 people in 20C4 ways
20C4 = (20)(19)(18)(17)/(4)(3)(2)(1)

The RATIO = (20)(19)(18)(17)(16)/(5)(4)(3)(2)(1)]/[(20)(19)(18)(17)/(4)(3)(2)(1)]
= (20)(19)(18)(17)(16)/(5)(4)(3)(2)(1)][(4)(3)(2)(1)/(20)(19)(18)(17)]
=(20)(19)(18)(17)(16)(4)(3)(2)(1)/(20)(19)(18)(17)(5)(4)(3)(2)(1)
=(20)(19)(18)(17)(16)(4)(3)(2)(1)/(20)(19)(18)(17)(5)(4)(3)(2)(1)
=16/5

Answer: C

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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