In a certain population, there are 3 times as many people aged twenty-one or under...

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Source: GMAT Paper Tests

In a certain population, there are 3 times as many people aged twenty-one or under as there are people over twenty-one. The ratio of those twenty-one or under to the total population is

A. 1 to 2
B. 1 to 3
C. 1 to 4
D. 2 to 3
E. 3 to 4

The OA is E
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BTGmoderatorLU wrote:
Mon Jun 22, 2020 12:59 pm
Source: GMAT Paper Tests

In a certain population, there are 3 times as many people aged twenty-one or under as there are people over twenty-one. The ratio of those twenty-one or under to the total population is

A. 1 to 2
B. 1 to 3
C. 1 to 4
D. 2 to 3
E. 3 to 4

The OA is E
A quick approach is to choose some numbers that meet the given conditions.

So, let's say that there is 1 person over twenty-one.

If there are 3 times as many people aged twenty-one or under as there are people over twenty-one, then there must be 3 people aged twenty-one or under.

This means the TOTAL population = 1 + 3 = 4

The ratio of those twenty-one or under to the total population = 3 to 4

Answer: E

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BTGmoderatorLU wrote:
Mon Jun 22, 2020 12:59 pm
Source: GMAT Paper Tests

In a certain population, there are 3 times as many people aged twenty-one or under as there are people over twenty-one. The ratio of those twenty-one or under to the total population is

A. 1 to 2
B. 1 to 3
C. 1 to 4
D. 2 to 3
E. 3 to 4

The OA is E
Solution:

We can let x = the number of people who are over 21 years old. Thus, the number of people who are 21 or under is 3x, and the total population is 4x. Therefore, the ratio of those twenty-one or under to the total population is:

3x : 4x = 3 : 4

Answer: E

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