Question

A bag contains 40 balls out of which x are white. If one ball is drawn at random the probability of drawing a white ball is y. Now place this ball and 20 more white balls in this bag. Now, if a ball is drawn from the bag the probability of drawing a white ball is 4y. Find x

Answer 1

Answer:

x = 4 white balls

Step-by-step explanation:

We are given,

Total number of balls = 40

No. of white balls = x

Thus,

Probability(of picking a white ball at random) = x/40

But given,

P(of picking a white ball at random) = y

∴ x/40 = y

x = 40y ------ 1

Now,

20 more white balls are added,

Thus,

Total balls = 40 + 20 = 60

Total white balls = x + 20

Now,

P(of picking white balls at random) = (x + 20)/60

But given,

P = 4y

∴ (x + 20)/60 = 4y

x + 20 = 60 × 4y

x + 20 = 240y

240y - x = 20

From eq.1 we get,

240y - (40y) = 20

200y = 20

y = 20/200

y = 1/10

Thus, from eq.1 we get,

x = 40(1/10)

x = 4 white balls

Thus,

At beginning, there were 4 white balls.

Hope it helped and believing you understood it........All the best