A total of 50 blue folders and red folders are in a container. The ratio of blue folders to red folders was 1 : 4. Some silver folders and black folders were put into the container. For every 2 red folders that were already in the container, 2 black ones were added. Then, the final number of blue folders and silver folders was ⁵₈ the final number of red folders and black folders. Find the total number of silver and black folders.

Silver folders	Blue folders	Red folders	Black folders
	1x1	4x1
		2x2	2x2
5x1		8x1
4 u	1 u	4 u	4 u

The number of red folders is repeated.  Make the number of red folders the same.  LCM of 4 and 2 is 4.

The total number of red folders and black folders is repeated.  Make the total number of red and black folders the same.  LCM of 8 and 8 is 8.

Total number of blue folders and red folders
= 1 u + 4 u
= 5 u

5 u = 50

1 u = 50 ÷ 5 = 10

Total number of silver and black folders
= 4 u + 4 u
= 8 u
= 8 x 10
= 80

Answer(s): 80