Question

In a bag, there are red and blue cubes in the ratio 4:7.

Sam adds 10 more red cubes to the bag.
Now there are red and blue cubes in the ratio 6:7.
How many blue cubes are in the bag?

Answer 1

x - red
y - blue


`(x)/(y)=(4)/(7)\\ (x+10)/(y)=(6)/(7)\\\\ 7x=4y\\ 7x+70=6y\\ 4y+70=6y\\ 2y=70\\ y=35\\\\ 7x=4\cdot35\\ 7x=140\\ x=20`