A fruit seller sells only starfruits and guavas. The ratio of starfruits to guavas is 1 : 2. A total of 144 fruits are added. The number of starfruits becomes 3 times as many as before and the number of guavas becomes 4 times as many as before. How many fruits are there at first?

	Comparing starfruits at first and in the end	Starfruits	Guavas	Comparing guavas at first and in the end
Before	1x1 = 1 u	1 u	2 u	1x2 = 2 u
Change		+ 144
After	3x1 = 3 u	3 u	8 u	4x2 = 8 u

The number of guavas at first is repeated.  Make the number of guavas at first the same.  LCM of 1 and 2 is 2.

The number of starfruits at first is repeated. Make the number of starfruits at first the same. LCM of 1 and 1 is 1.

Number of fruits at first
= 1 u + 2 u
= 3 u

Number of fruits in the end
= 3 u + 8 u
= 11 u

Number of fruits added
= 11 u - 3 u 
= 8 u

8 u = 144

1 u = 144 ÷ 8 = 18

Number of fruits at first
= 3 u
= 3 x 18
= 54

Answer(s): 54