Question

A bag of marbles has 15 blue, 18 green, 6 yellow, and 10 red marbles. How many marbles need to be added to the bag so the probability of drawing a red marble is 20% or 1/5

Answer 1

1 marble needs to be added

Explanation:

So we know that there are 15 blue marbles, 18 green, 6 yellow, and 10 red. We are trying to find out how may marbles must be added to the bag so that there is a 1/5 or 20% chance of drawing a red marble. Lets find out how many marbles should be in the bag (NOT added to the bag, we will find that later) so that the chance of drawing a red one is 1/5. To do this, we can make this equation:

`(10)/(T)=(1)/(5)`

Where T is the total number of marbles that should be in the bag. Lets solve this for T:

`(10)/(T)=(1)/(5)`

Cross multiply.

T = (10)(5)

T = 50

So now we know that the total number of marbles that should be in the bag to make the chance of drawing a red 1/5 is 50. Now we can subtract the number of marbles that are currently in the bag from 50 to find the number of marbles to add.

50 - (15 + 18 + 6 + 10) = 50 - 49 = 1

So 1 marbles has to be added so that the chance of drawing a red marble is 1/5.

I hope you find my answer and explanation helpful. Happy studying. :)

Answer 2

One marble (other than red)

Explanation:

The total number of marbles is 15 + 18 + 6 + 10 = 49. The probability of drawing a red marble is 10 out of 49. We want to change those odds to 10 out of 50 (or 20%). Therefore, we need to add one marble; any color other than red will work.