If there are sixty-five dolphins in the ocean, and three times that number joins in from a river which has its mouth at the ocean, calculate the total number of dolphins in the ocean.
Let’s work this out in a step by step way to be sure we have the right answer.
260
When three times the number of dolphins in the ocean joins in from a river, the number of dolphins in the ocean increases by 3 * 65 = 195.

The total number of dolphins in the ocean increases to 195 + 65 = 260.

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Thus, the answer is 260