r/(b+r) * b/(b+r-1) = .28
.5 * b/(b+r-1) = .28
b/(b+r-1) = .56
See where that takes you, given what you know about conditional probabilities.
A BOY CONTAINS RED AND BLUE MARBLES ,TWO MARBLES ARE DRAWN WIHT OUT REPLACEMENT.THE PROBABLILITY OF SELECTING A RED MARBLE ANDTHEN A BLUE MARBLE IS 0.28,THE PROBABILITY OF SELECTING A RED MARBLE ON THE FIRST DRAWNIS 0.5, WHAT IS THEPROBABILITY OF SELCTING A BLUE MARBLE ON THE SECOND DRAW,GIVEN THE FIRST MARBLE DRAWN WAS RED?
1 answer
1 answer