Question

A bag contains 100 marbles which are red, green, and blue. Suppose a student randomly selects a marble without looking, records the color, and then places the marble back in the bag. The student has recorded 7 red marbles, 2 green marbles and 11 blue marbles. Predict how many red marbles are in the bag.

Answer 1

35 red marbles

Explanation:

The total number of marbles the student recorded is 20

Now we have to make a ratio of red to the total number of marbles

That would be 7 : 20

After this, there will be a new ratio which is x : 100

Lastly we will solve for x making the equation 20x = 700, x = 35

Answer 2

35 red marbles

Explanation:

So we can put the different color marbles in a ratio. So 7:2:11. If we add all of those up we get 20. We do 100/20 to get 5. Each number in the ratio is equivalent to 5 marbles. Then we do 7*5 to get 35. We can check our work by doing, (7*5) + (2*5) + (11*5) = 100. And it does equal 100 so the answer is correct.