Three years ago men made up two out of every three internet users in America. Today the ratio of male to female users is about 1 to 1. In that time the number of American females using the internet has grown by 30,000,000, while the number of males who use the internet has grown by 100%. By how much has the total internet-user population increased in America in the past three years?
 |
50,000,000 | ||
 |
60,000,000 | ||
 |
80,000,000 | ||
 |
100,000,000 | ||
 |
200,000,000 |
Let x = the number of female internet users three years ago.
Since two out of three users back then were men, we know that for every female user, there were two male users. Therefore, the number of male users three years ago would be 2x.
The percent of male users has increased by 100%. Therefore the number of male users now would be 4x. The number of female users has increased by 30,000,000; therefore the number of current female users would be x + 30,000,000.
The ratio of male to female users is now 1:1. We can therefore solve for x as follows:
4x = x + 30,000,000
3x = 30,000,000
x = 10,000,000.
This means that three years ago there were 10,000,000 (x) female users, and 20,000,000 (2x) male users. This is a total of 30,000,000 users. Today, there are 40,000,000 (4x) male users and 40,000,000 (x + 30,000,000) female users, for a total of 80,000,000 users. This is an increase of 50,000,000 users. The answer is (A).
source: number2.com
