Answer
Estimate: 200 million; Exact: 167 million
Work Step by Step
To estimate, we round each number to the nearest hundred million, so 311 million rounds to 300 million and 478 million rounds to 500 million. We subtract 500 million - 300 million to get an estimated increase of 200 million. The exact difference is 478 million - 311 million = 167 million.