AbdurRakib wrote:

City X has a population 4 times as great as the population of City Y, which has a population twice as great as the population of City Z. What is the ratio of the population of City X to the population of City Z?

A) 1:8

B) 1:4

C) 2:1

D) 4:1

E) 8:1

We are given that City X has a population 4 times as great as the population of City Y and that City Y has a population twice as great as the population of City Z.

If we let the population of City X = x, the population of city Y = y, and the population of city Z = z, we can create the following equations:

x = 4y

AND

y = 2z

We need to determine the ratio of the population of City X to the population of City Z, or x/z.

To determine the ratio, we can get both x and z in terms of y, so we have:

x = 4y and z = y/2.

We can substitute 4y for x and y/2 for z in the ratio x/z:

(4y)/(y/2) = (4y)(2/y) = 8.

Thus, the ratio is 8 : 1.

Answer: E

_________________

Scott Woodbury-Stewart

Founder and CEO

GMAT Quant Self-Study Course

500+ lessons 3000+ practice problems 800+ HD solutions