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In 1984 a certain union had a total of 15,600 members. Was t

by Anaira Mitch » Thu Feb 16, 2017 5:47 pm
In 1984 a certain union had a total of 15,600 members. Was the percent increase in the total number of members in the union from 1984 to 1985 greater than that from 1985 to 1986 ?

(1) From 1984 to 1985 the total number of members in the union increased by 781, and from 1985 to 1986 the total number of members in the union again increased by 781.

(2) In 1985 the union had a total of 16,381 members, and in 1986 the union had a total of 17,162 members.
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Source: — Data Sufficiency |
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by GMATGuruNY » Thu Feb 16, 2017 6:25 pm
Anaira Mitch wrote:In 1984 a certain union had a total of 15,600 members. Was the percent increase in the total number of members in the union from 1984 to 1985 greater than that from 1985 to 1986 ?

(1) From 1984 to 1985 the total number of members in the union increased by 781, and from 1985 to 1986 the total number of members in the union again increased by 781.

(2) In 1985 the union had a total of 16,381 members, and in 1986 the union had a total of 17,162 members.
Statement 1:
Since we know how the TOTAL increased from 1984 to 1985 (from 15600 to 15600+781) and how the total increased from 1985 to 1986 (from 15600+781 to 15600+781+781), we can calculate the percent increase for each period, allowing us to determine whether the percent increase from 1984 to 1985 was greater than that from 1985 to 1986.
SUFFICIENT.

Statement 2:
Since we know how the TOTAL increased from 1984 to 1985 (from 15600 to 16381) and how it increased from 1985 to 1986 (from 16381 to 17162), we can calculate the percent increase for each period, allowing us to determine whether the percent increase from 1984 to 1985 was greater than that from 1985 to 1986.
SUFFICIENT.

The correct answer is D.
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by Jay@ManhattanReview » Thu Feb 16, 2017 8:25 pm
Anaira Mitch wrote:In 1984 a certain union had a total of 15,600 members. Was the percent increase in the total number of members in the union from 1984 to 1985 greater than that from 1985 to 1986 ?

(1) From 1984 to 1985 the total number of members in the union increased by 781, and from 1985 to 1986 the total number of members in the union again increased by 781.

(2) In 1985 the union had a total of 16,381 members, and in 1986 the union had a total of 17,162 members.
We have members in 1984 = 15,600.

Let's take each statement one by one.

S1: From 1984 to 1985 the total number of members in the union increased by 781, and from 1985 to 1986 the total number of members in the union again increased by 781.

We see that the INCREASE '781' is a constant for each period: 1984-1985 and 1985-1986.

Percentage increase for the period 1984-1985 = [781/15600]*100% ---(1)

Percentage increase for the period 1985-1986 = [781/(15600+781)]*100% ---(2)

We see that the denominator for (2) is greater than that for (1), thus, the percentage increase for the period 1984-1985 would be greater than the percentage increase for the period 1985-1986. The answer is Yes. Sufficient.

S2: In 1985 the union had a total of 16,381 members, and in 1986 the union had a total of 17,162 members.

We have:

Members in 1984 = 15,600,
Members in 1985 = 16,381; Increase = 16,381 - 15,600 = 781.
Members in 1986 = 17,162; Increase = 17,162 - 16,381 = 781.

We see that statement 2 is a rephrased version of statement 1, which itself is sufficient.

The correct answer: D

Hope this helps!

-Jay

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by Scott@TargetTestPrep » Mon Feb 27, 2017 10:44 am
Anaira Mitch wrote:In 1984 a certain union had a total of 15,600 members. Was the percent increase in the total number of members in the union from 1984 to 1985 greater than that from 1985 to 1986 ?

(1) From 1984 to 1985 the total number of members in the union increased by 781, and from 1985 to 1986 the total number of members in the union again increased by 781.

(2) In 1985 the union had a total of 16,381 members, and in 1986 the union had a total of 17,162 members.
We are given that in 1984 a certain union had a total of 15,600 members. We need to determine whether the percentage increase in the total number of members in the union from 1984 to 1985 was greater than the increase from 1985 to 1986.

Statement One Alone:

From 1984 to 1985 the total number of members in the union increased by 781, and from 1985 to 1986 the total number of members in the union again increased by 781.

Since there were 15,600 members in 1984, there were 15,600 + 781 = 16,381 members in 1985 and 16,381 + 781 = 17,162 members in 1986.

Since we have the number of members in 1984, 1985, and 1986, we have enough information to determine whether the percentage increase in the total number of members in the union from 1984 to 1985 was greater than the increase from 1985 to 1986. Statement one alone is sufficient to answer the question.

Statement Two Alone:

In 1985 the union had a total of 16,381 members, and in 1986 the union had a total of 17,162 members.

Once again, since we have the number of members in 1984, 1985, and 1986, we have enough information to determine whether the percentage increase in the total number of members in the union from 1984 to 1985 was greater than the increase from 1985 to 1986. Statement two alone is sufficient to answer the question.

Answer: D

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by [email protected] » Mon Feb 27, 2017 1:07 pm
Hi Anaira Mitch,

Certain DS questions are essentially just 'logic' questions - you don't really have to do any math to get to the correct answer as long as you understand the concepts involved (and what you really 'need' to answer the specific question that is asked.

In this prompt, we're given the number of members in the union in 1984. We're asked if the percent increase in members from 1984 to 1985 was greater than the percent increase in members from 1985 to 1986. This is a YES/NO question.

1) From 1984 to 1985 the total number of members in the union increased by 781, and from 1985 to 1986 the total number of members in the union again increased by 781.

With the information in Fact 1, we can find the total membership in 1985 and in 1986, so we CAN calculate the percent increase for each of the two time periods. Once we have that information, then we can definitively answer the question.
Fact 1 is SUFFICIENT.

(2) In 1985 the union had a total of 16,381 members, and in 1986 the union had a total of 17,162 members.

With the information in Fact 2, we can have the total membership in 1985 and in 1986, so we CAN calculate the percent increase for each of the two time periods. Once we have that information, then we can definitively answer the question.
Fact 2 is SUFFICIENT.

Final Answer: D

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