Explain simply why 88 is the correct answer to: In a big box, there are marbles in 4 colors. Inside, there are 20 red marbles. There are three times more green marbles than red. Yellow marbles make up 20% of the green marbles. How many marbles are of a different color if the total of all marbles in the box is three times more than the number of green marbles?. Explanation:
There are 3 * 20 = 60 green marbles. There are 60 * 20 / 100 = 12 yellow marbles. In total there are 3 * 60 = 180 marbles. That leaves 180 - 20 - 60 - 12 = 88 marbles of another color in the box.