Question

In a certain town, 25% of people commute to work by bicycle. If a person is selected randomly from the town, what are the odds against selecting someone who commutes by bicycle?
1:3

3:1

1:4

3:4

Answer 1

Answer b is the correct answer. 3.1

Answer 2

Answer: Choice B)   3:1

=============================================================

Explanation:

Consider a very small town of only 4 people.

If 1 person bikes to work, then 1/4 = 0.25 = 25% of the population commutes by bicycle. We see that the remaining 4-1 = 3 people don't travel by bike.

The odds against selecting someone who uses their bike to get to work is 3:1 which is why the answer is choice B

We list the number of people we don't want first, and then the number of people we do want (those who use a bike). A colon separates the two values to form the odds ratio.

We can say "3:1" as "3 to 1". It means we're 3 times more likely to select someone we don't want vs someone we do want. The odds are against the bike person which is why the value we don't want is listed first.

In contrast, if your teacher asked "what are the odds in favor of selecting someone who commutes by bicycle?" then the answer would be 1:3. We simply swap the positions of what we set up earlier.