# 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?

##### 1 Answer

Feb 18, 2017

Then number of red marbles removed were

#### Explanation:

Given -

Red marbles

Green marbles

Total no of marbles

Number of Marbles removed

Marbles in the box

Probability of drawing one green marble is

Among the remaining 6 marbles,

Then Probability of drawing one green marble is = number of green marbles / Total Number of marbles.

We know

Then -

#x/6=0.5#

#x=0.5xx 6=3#

After 5 marbles are removed from the box, the number of green marbles remaining is 3.

It means out of 4 green marbles, one green marble has been removed.

Out of 5 marbles one marble is green. Then the other four must be red.

Then number of red marbles removed were