4 red marbles were removed from the box .
Step-by-step 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 , [tex]11-5 = 6[/tex] marbles ,So probability of drawing a green marble is now 0.5 i.e.
⇒ [tex]\frac{x}{6}=0.5[/tex]
⇒ [tex]\frac{x}{6}(6)=0.5(6)[/tex]
⇒ [tex]x=3[/tex]
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 .
