A fruit seller sells only peaches and kiwis. The ratio of peaches to kiwis is 4 : 5. A total of 36 fruits are added. The number of peaches becomes 3 times as many as before and the number of kiwis becomes 3 times as many as before. How many fruits are there in the end?

	Comparing peaches at first and in the end	Peaches	Kiwis	Comparing kiwis at first and in the end
Before	1x4 = 4 u	4 u	5 u	1x5 = 5 u
Change		+ 36
After	3x4 = 12 u	12 u	15 u	3x5 = 15 u

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

The number of peaches at first is repeated. Make the number of peaches 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
= 12 u + 15 u
= 27 u

Number of fruits added
= 27 u - 9 u 
= 18 u

18 u = 36

1 u = 36 ÷ 18 = 2

Number of fruits in the end
= 27 u
= 27 x 2
= 54

Answer(s): 54