The answer is 10 drinks. This is the example of a simple proportion. 10 bottles will be changed for 1 drink. 100 bottles will be changed for x drinks. Make the proportion. 10 bottles : 1 drink = 100 bottles : x. Rearrange it. 10 bottles x = 100 bottles 1 drink. Express it for x. x = 100 bottles * 1 drink : 10 bottles. x = 10 drinks. So, for 100 bottles you will get 10 drinks.