Maria has type B blood She can safely receive blood transfus

Maria has type B blood.

She can safely receive blood transfusions from people with blood types O and B.
What is the probability that a randomly chosen American can donate blood to Maria?
Give your answer to two decimal places.
Fill in the blank:
The probability that a randomly chosen American can donate blood to Maria is

Solution

considering blood to be of types A,B,AB and O

further all blood groups are equi probable

probabilty of blood type A =probabilty of blood type B = probabilty of blood type AB =probabilty of blood type O =x

probabilty of blood type A +probabilty of blood type B+probabilty of blood type AB+probabilty of blood type O =1

=>4x=1

=>x=1/4

probabilty that a random person will have blood of type B or O = x+x

=1/4+1/4

=1/2

= 0.50