A fruit seller sells only passion fruits and mangoes. The ratio of passion fruits to mangoes is 4 : 5. A total of 330 fruits are added. The number of passion fruits becomes 4 times as many as before and the number of mangoes becomes 3 times as many as before. How many fruits are there at first?

	Comparing passion fruits at first and in the end	Passion Fruits	Mangoes	Comparing mangoes at first and in the end
Before	1x4 = 4 u	4 u	5 u	1x5 = 5 u
Change		+ 330
After	4x4 = 16 u	16 u	15 u	3x5 = 15 u

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

The number of passion fruits at first is repeated. Make the number of passion fruits 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
= 16 u + 15 u
= 31 u

Number of fruits added
= 31 u - 9 u 
= 22 u

22 u = 330

1 u = 330 ÷ 22 = 15

Number of fruits at first
= 9 u
= 9 x 15
= 135

Answer(s): 135