A fruit seller sells only persimmons and mangosteens. The ratio of persimmons to mangosteens is 4 : 5. A total of 140 fruits are added. The number of persimmons becomes 2 times as many as before and the number of mangosteens becomes 3 times as many as before. How many fruits are there at first?

	Comparing persimmons at first and in the end	Persimmons	Mangosteens	Comparing mangosteens at first and in the end
Before	1x4 = 4 u	4 u	5 u	1x5 = 5 u
Change		+ 140
After	2x4 = 8 u	8 u	15 u	3x5 = 15 u

The number of mangosteens at first is repeated.  Make the number of mangosteens at first the same.  LCM of 1 and 5 is 5.

The number of persimmons at first is repeated. Make the number of persimmons at first the same. LCM of 1 and 4 is 4.

Number of fruits at first
= 4 u + 5 u
= 9 u

Number of fruits in the end
= 8 u + 15 u
= 23 u

Number of fruits added
= 23 u - 9 u 
= 14 u

14 u = 140

1 u = 140 ÷ 14 = 10

Number of fruits at first
= 9 u
= 9 x 10
= 90

Answer(s): 90