A fruit seller sells only starfruits and mangoes. The ratio of starfruits to mangoes is 3 : 5. A total of 357 fruits are added. The number of starfruits becomes 3 times as many as before and the number of mangoes becomes 4 times as many as before. How many fruits are there in the end?

	Comparing starfruits at first and in the end	Starfruits	Mangoes	Comparing mangoes at first and in the end
Before	1x3 = 3 u	3 u	5 u	1x5 = 5 u
Change		+ 357
After	3x3 = 9 u	9 u	20 u	4x5 = 20 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 starfruits at first is repeated. Make the number of starfruits at first the same. LCM of 1 and 3 is 3.

Number of fruits at first
= 3 u + 5 u
= 8 u

Number of fruits in the end
= 9 u + 20 u
= 29 u

Number of fruits added
= 29 u - 8 u 
= 21 u

21 u = 357

1 u = 357 ÷ 21 = 17

Number of fruits in the end
= 29 u
= 29 x 17
= 493

Answer(s): 493