Question

At Michael's school, 38% of the students have a pet dog and 24% of the students have a pet cat. Michael found that 11% of the students
had both a pet dog and a pet cat.
What is the probability that a randomly chosen student at Michael's school will have a pet dog or a pet cat?
A. 62%
B. 51%
C. 40%
D. 83%

Answer 1

I find it easiest to draw a venn-diagram for this kind of question but the answer isn’t too complicated.
11% of the students have a pet dog AND a pet cat. Because of this you want to take away 11% from the percentage of students with a pet dog and also from the percentage with a pet cat. This is because 11% of the students with a pet dog also have a pet cat and vice-versa and you don’t want to count any students twice.
Once you’ve done this it’s very simple, just add up your values, so 11 + (38 - 11) + (24 - 11) which will give you 51.
Hope this helps

Answer 2

the answer is going to be c40