Goldman Sachs on Tuesday reported a monster jump in its third quarter earnings, reaping $3 billion in profits — far higher than what Wall Street analysts had expected.

How did the investment bank do it? The steadying economic environment helped — but so did a financial maneuver employed by Goldman’s chief executive, David M. Solomon, a few weeks ago.

In early September, Mr. Solomon publicly sounded the alarm, saying many aspects of the bank’s business were stumbling in the third quarter. He warned that the bank’s upcoming earnings might disappoint.

They didn’t — not at Goldman nor the two other major banks that reported results on Tuesday.

Up first, a billion-dollar beat

Goldman pulled in nearly $13 billion in revenue during the third quarter, over $1 billion more than projections.

The bank’s $3 billion in quarterly profit was roughly equal to what it pulled in during the previous quarter, despite Mr. Solomon’s warning last month that profits might not hold up as well as they had in the first half of the year.

A bank executive, briefing reporters on the condition of anonymity, said that trading activity — a core part of any investment bank — came in stronger than expected in September, the same period that the Federal Reserve announced a large cut in interest rates.