Question

16

A box contains 11 marbles—7 red and 4 green.
Five of these marbles are removed at random.
If the probability of drawing a green marble is
now 0.5, how many red marbles were removed
from the box?

Answer 1

4 red marbles were removed from the box .

Explanation:

Here we have , A box contains 11 marbles—7 red and 4 green. Five of these marbles are removed at random. If the probability of drawing a green marble is now 0.5, We need to find how many red marbles were removed from the box .Let's find out:

Let number of green marbles removed be x , According to question , after removing 5 marbles we now have ,
`11-5 = 6` marbles ,So probability of drawing a green marble is now 0.5 i.e.

⇒
`(x)/(6)=0.5`

⇒
`(x)/(6)(6)=0.5(6)`

⇒
`x=3`

So , Number of green marbles left is 3 after removal of 5 marbles from box that means only 1 green marble is removed and , 4 red marbles are removed .

Therefore , 4 red marbles were removed from the box .