Question

A bag contains one green marble, two yellow marbles, four blue marbles and five red marbles. How many blue marbles would you need to add to make the probability of drawing a blue marble 1/2?

Answer 1

Explanation:

Since there is 1 green, 2 yellow, 4 blue, and 5 red we start with 12 marbles. For the probability of picking a blue to be 1/2 we must satisfy.

(b+x)/(12+x)=1/2. (Where x is the number of blue marbles added)

2(b+x)=12+x

2b+2x=12+x

2b+x=12

x=12-2b, since we started with 4 blue marbles

x=12-2(4)

x=12-8

x=4

So we would need to add 4 blue marbles to make the probability of picking a blue 1/2.

Answer 2

You would have to add 4 blue marbles

Explanation:

there are a total of 12 marbles, 4 of them being blue.

If you add 4 blue ones, there would be a total of 16 marbles and 8 of them would be blue.

8/16 = 1/2

Therefore, 4 blue marbles need to be added for the chance to draw one to be 1/2 or 50%