There are 8 boys and 5 girls in a class. If four students are selected at random, what is the probability that 2 girls and 2 boy are selected?
8C2 *5C2/13C4 =8*7*5*4*4*3*2/(2*2*13*12*11*10)=0.3916
There are 12 boys and 9 girls in a class. If three students are selected at random, what is the probability that 1 girl and 2 boys are selected?
Two digits are selected at random from digits 1 through 9. If sum is even, find the probability that both numbers are odd?
Three points are selected at random on a sphere's surface. What is the probability that they all lie in the same hemisphere? Assume that the great circle, bordering a hemisphere, is part of the hemisphere.
