Question

a bag contains 8 white and some black balls if the probability of drawing a black ball from the bag is four times that of a white ball find number of black balls in the bag

Answer 1

Hope this answer will help u.........

Answer 2

Answer:

2 black balls

Step-by-step explanation:

Let number  black balls be denoted as $x$

Then the number of a white balls is $4*x=4x$

If 8 balls give  4x, what number of balls give  x?

$4x=8\\x=?$

Cross-multiplying we get

$x=\frac{8}{4}\\ x=2$

Therefore, there are 2 white balls.

This gives probability of drawing a black ball as

$\frac{2}{2+8}=\frac{1}{5}$

thus probability of drawing a white ball would be

$4*\frac{1}{5}=\frac{4}{5}$

also given as $\frac{8}{2+8}=\frac{8}{10}=\frac{4}{5}$