A fruit seller sells only kiwis and peaches. The ratio of kiwis to peaches is 3 : 5. A total of 39 fruits are added. The number of kiwis becomes 2 times as many as before and the number of peaches becomes 3 times as many as before. How many fruits are there at first?

	Comparing kiwis at first and in the end	Kiwis	Peaches	Comparing peaches at first and in the end
Before	1x3 = 3 u	3 u	5 u	1x5 = 5 u
Change		+ 39
After	2x3 = 6 u	6 u	15 u	3x5 = 15 u

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

The number of kiwis at first is repeated. Make the number of kiwis 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
= 6 u + 15 u
= 21 u

Number of fruits added
= 21 u - 8 u 
= 13 u

13 u = 39

1 u = 39 ÷ 13 = 3

Number of fruits at first
= 8 u
= 8 x 3
= 24

Answer(s): 24