A total of 36 pink notebooks and blue notebooks are in a container. The ratio of pink notebooks to blue notebooks was 1 : 2. Some grey notebooks and purple notebooks were put into the container. For every 1 blue notebooks that were already in the container, 4 purple ones were added. Then, the final number of pink notebooks and grey notebooks was ⁴₅ the final number of blue notebooks and purple notebooks. Find the total number of grey and purple notebooks.

Grey notebooks	Pink notebooks	Blue notebooks	Purple notebooks
	1x1	2x1
		1x2	4x2
4x2		5x2
7 u	1 u	2 u	8 u

The number of blue notebooks is repeated.  Make the number of blue notebooks the same.  LCM of 2 and 1 is 2.

The total number of blue notebooks and purple notebooks is repeated.  Make the total number of blue and purple notebooks the same.  LCM of 10 and 5 is 10.

Total number of pink notebooks and blue notebooks
= 1 u + 2 u
= 3 u

3 u = 36

1 u = 36 ÷ 3 = 12

Total number of grey and purple notebooks
= 7 u + 8 u
= 15 u
= 15 x 12
= 180

Answer(s): 180