Question

A bag contains 120 marbles. Some are red and the rest are black. There are 19 red marbles for every black marble. How many red marbles are in the bag?

Answer 1

There are 114 red marbles.

Explanation:

We can make a smaller sample of the problem to help evaluate the big one. For every 19 red, there is 1 black. That means the sample size is 20 in total since 19+1 is 20. In other words, for every 20 marbles, 19 of them are red.

Now we can look at the size of 120. 20 goes into 120 6 times. That means there are 6 times as many red marbles. 19x6=114.

There are 114 red marbles.

Answer 2

114 red marbles

Explanation:

red: black: total

19 1 19+1 = 20

We have 120 marbles

120/20 = 6

Multiply each by 6

red: black: total

19 *6 1*6 20*6

114 6 120