200 elementary school students were surveyed to find their blood groups. Of those, 55 were of blood group A, 85 of blood group B, and 21 of blood group O.

What is the probability that a randomly chosen student has either blood group A or blood group B?
A)
0.25
B)
0.60
C)
0.70
D)
0.81

B?

I like C, since there are 140/200 of the students with A or B blood.

or C.

Thank you :)

To find the probability that a randomly chosen student has either blood group A or blood group B, we need to calculate the proportion of students with blood group A or blood group B out of the total number of students surveyed.

Given that there are 200 students surveyed, we can use the formula:

P(A or B) = P(A) + P(B) - P(A and B)

P(A) = Number of students with blood group A / Total number of students
P(B) = Number of students with blood group B / Total number of students
P(A and B) = Number of students with both blood group A and blood group B / Total number of students

From the information given in the question, there are 55 students with blood group A, 85 students with blood group B, and no information about the number of students with both blood group A and blood group B.

Plugging in the values into the formula:

P(A or B) = 55/200 + 85/200 - 0/200

Simplifying:

P(A or B) = (55 + 85 - 0)/200
P(A or B) = 140/200
P(A or B) = 0.7

Therefore, the probability that a randomly chosen student has either blood group A or blood group B is 0.7.

The correct option is C) 0.70.