A jar holds red and blue marbles in a ratio of 5:3. After removing 15 blue marbles, the ratio of red to blue marbles changes to 5:2. How many red marbles are there in the jar?
Show answer & explanation
Correct answer: D
Explanation
Given:
Red : Blue = 5 : 3
15 blue marbles were drawn
New ratio = 5 : 2
Let's say initially
Red = 5x
Blue = 3x
After 15 blue marbles were drawn
Blue = 3x − 15
New ratio
5x : (3x − 15) = 5 : 2
2(5x) = 5(3x − 15)
10x = 15x − 75
5x = 75
x = 15
Red marbles = 5x = 5 × 15 = 75
There are 75 red marbles in the jar.