Question

box contains 20 balls in which some are blue and other are red if the probability a blue ball is 1÷4, then find the number of red balls in the box​

Answer 1

If the probability of blue ball is 1/4 then that of red will be 3/4.

Therefore the number of red balls is 3/4×20=15

Answer 2

The sum of probability should always be 1.

So here the probability of blue ball = 1/4

So the probability of red ball = 1 - 1/4 = 3/4

So, Number of red balls = Probability of red ball * Total number of balls

= 3/4 * 20 = 3*5 = 15

There are 15 red balls in the box