# Probability - Word Problem

#### NReidel61

##### New member
Any help would be much appreciated! I don't just want answers I would like an explanation on how to achieve the answer. I can't seem to understand this probability. Again, any help would be amazing! I really need to understand this. Thanks!!!

About 26% of orthopedic surgeries involves knee problems. The following table summarizes data collected from a sample of adults who have knee surgery. (Source:

Age Full Knee Replacement No Knee Replacement
18 - 44 2 9
45 - 64 25 11
65 – 74 43 27
75 – 84 27 14
85 - older 3 2

1) What is the probability that an orthopedic surgical case selected at random involves
knee surgery?
It's hard to believe you are serious. You were told "About 26% of orthopedic surgeries involves knee problems." Do you not know what that means?
2) What is the probability that a person from ages 18 – 44 who has knee surgery has a
full knee replacement?
How many people are listed in the 18-44 category? How many of those had full knee replacement? What percentage was that? Do you know how a "percentage" is related to a "probability"?
3) What is the probability that a person from 45 – 64 who has knee surgery has a full
knee replacement?
Same as (2)!
4) What is the probability that a person who has knee surgery has a full knee
replacement?
How many total people had knee surgery? How many had full knee surgery? What percentage is that?