A worker in a factory earns $10 an hour. The worker works 10 hours a day for 10 days straight before a vacation. How much money did the worker earn before going on vacation?

The worker earns $10 per hour and works for 10 hours a day, so the worker earns $10 x 10 = $<<10*10=100>>100 per day.

The worker earns $100 per day and works for 10 days, so the worker earns $100 x 10 = $<<100*10=1000>>1000 before going on vacation. Answer: \boxed{1000}.

pick between 10, 10 x 10 x 10, 10 x 10, 3 x 3 x 3 x 3 x 3 x 3 x 3 x 3 x 3 x 3

Between the given options, the largest number is 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 which is equal to 10,000,000,000. Therefore, the largest number is \boxed{10,000,000,000}.