Question

A bag contains 6 red balls and some black balls. If the ratio of the probabilities of drawing a red ball to black is 3:4,find the (i) number of black balls (ii) probability of either a black ball

Answer 1

red balls = 6

black balls = 8

i)8 balls

ii)8/14=4/7

hope 9t helps

Answer 2

I think it is important to note here that the order in which balls are chosen does not matter.

The total number of ways of drawing 2 balls out of 7 is 7C2 i.e. 21

For first case we either draw 2 red (3C2) or 2 blue balls (4C2), for total favorable cases of 9

Hence probability of drawing same color balls is 921

The probability of drawing different color balls is therefore 1−921=1221