A shopkeeper has two types of rice having the rates of 50 per kg and 30 per kg. He mixed both types such that by selling the mixture at 49.5 per kg, there may be a gain of 10 percent. Find the ratio in which both types of rice are mixed.
1
2 : 1
2
3 : 1
3
4 : 5
4
1 : 2
5
2 : 7