Danny has 3 bottles of soda. He drinks 90% of one bottle and gives 70% of the other two bottles to his friends. How much soda does Danny have left, expressed as a percentage of a bottle? Let's think first. Chain of thought:
First find how much soda Danny drank: 1 bottle * .9 = .9 bottles. Then find how much soda Danny gave to his friends: 2 friends * 1 bottle / friend * .7 = 1.4 bottles. Now subtract the soda drunk and given away to find the remaining amount of soda: 3 bottles - .9 bottles - 1.4 bottles = .7 bottles * 100% = 70%.
Therefore, the answer is 70.