Question

A bag contains several colored balls. 28 of the are red. If a ball is drawn at random, the probability of drawing a red ball is 4/9. If x balls are added into the box. A ball is then drawn at random. If the probability of getting a red ball now is 1/2 then what is x

Answer 1

Step-by-step explanation:

Initial Probability is 4/9.

Red balls = 28

lets total balls be T

so 28/T = 4/9

hence by solving T = 9x28/4 = 63

now X ball are added to the lot and the Probability has increased from 4/9 to 1/2 hence there are some red balls in x. now for the minimum number of x all the balls should be red. now according to the question

total red balls/ total balls = 1/2

28+x/x+63 =1/2

2x + 56 = x + 63

x = 63 - 56 = 7

hence X is 7.

Answer 2

Answer:

Let no. of extra balls added= x

no. of balls is y

So, => 28/28+y= 4/9

=> 256/(28+y)= 4

=> 1/28+y= 1/64

=> 28+y=64

=> y= 46

Total no. of balls after adding x= 46+x

So,28/46+x= 1/2

46+x=56

=>x=10