Question

of 1000 students, 530 were boys and 180 had bicycles. of those who had bicycles, 30 were girls. what is the probability that a student surveyed was a boy or had a bicycle?

Answer 1

We have to compute the number of student that "are boys
or that have a bicycle"
There is 530 boys.
We have to add to the above number girls with bicycle, 30.
530+30=560.
The probability is the the above number of possibilities over 
the whole number of student:
$\frac{560}{1000}=0.56$
The probability is 0.56.