A total of 270 brown rulers and black rulers are in a container. The ratio of brown rulers to black rulers was 1 : 2. Some yellow rulers and red rulers were put into the container. For every 9 black rulers that were already in the container, 5 red ones were added. Then, the final number of brown rulers and yellow rulers was ⁴₇ the final number of black rulers and red rulers. Find the total number of yellow and red rulers.

Yellow rulers	Brown rulers	Black rulers	Red rulers
	1x9	2x9
		9x2	5x2
4x4		7x4
7 u	9 u	18 u	10 u

The number of black rulers is repeated.  Make the number of black rulers the same.  LCM of 2 and 9 is 18.

The total number of black rulers and red rulers is repeated.  Make the total number of black and red rulers the same.  LCM of 28 and 7 is 28.

Total number of brown rulers and black rulers
= 9 u + 18 u
= 27 u

27 u = 270

1 u = 270 ÷ 27 = 10

Total number of yellow and red rulers
= 7 u + 10 u
= 17 u
= 17 x 10
= 170

Answer(s): 170