A fruit seller sells only mangoes and starfruits. The ratio of mangoes to starfruits is 1 : 2. A total of 51 fruits are added. The number of mangoes becomes 2 times as many as before and the number of starfruits becomes 2 times as many as before. How many fruits are there in the end?

	Comparing mangoes at first and in the end	Mangoes	Starfruits	Comparing starfruits at first and in the end
Before	1x1 = 1 u	1 u	2 u	1x2 = 2 u
Change		+ 51
After	2x1 = 2 u	2 u	4 u	2x2 = 4 u

The number of starfruits at first is repeated.  Make the number of starfruits at first the same.  LCM of 1 and 2 is 2.

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

Number of fruits at first
= 1 u + 2 u
= 3 u

Number of fruits in the end
= 2 u + 4 u
= 6 u

Number of fruits added
= 6 u - 3 u 
= 3 u

3 u = 51

1 u = 51 ÷ 3 = 17

Number of fruits in the end
= 6 u
= 6 x 17
= 102

Answer(s): 102