TOKYO — By the time she accounted for the mixed-zone interview, her warm-down, the standard postrace drug testing, the news conference and the bus rides from Tokyo Aquatics Centre to the Olympic Village and back, Katie Ledecky figured she would have about 2½ hours between Monday’s sessions at the Tokyo Olympics swim meet for a quick bite to eat and a nap.

And then, by evening, she would be back in the pool for another 1,700 meters of racing.

Few beyond Ledecky would even attempt such a marathon day of swimming at these Olympics — a 400-meter freestyle final in the morning and a 200 free/1,500 free “double” in preliminary heats in the evening session, those last races separated by about two hours — let alone pull it off the way she did.

“I’ll sleep well tonight, I’ll tell you that,” she said when it was over. “I was just happy how it went, happy it’s over, and I got the job done.”

Ledecky earned her first medal of these Games on Monday morning, taking silver in the 400 free behind Australia’s Ariarne Titmus in a memorable duel in which Titmus caught and passed Ledecky in the final 100 meters to win the gold. It was the first time Ledecky had been beaten in five individual finals across three Olympic Games.

If Ledecky was feeling any adverse effects from the taxing 400 final, she didn’t show it Monday night when she climbed back on the blocks for the prelims of the 200 at 7:05 p.m. Tokyo time. She reeled off a time of 1 minute 55.28 seconds to claim the top overall seed, which she will take into Tuesday’s semifinals. Her time, which featured a blistering final 50 of 29.13, was the sixth-fastest in the world this year.

Titmus finished fourth overall in qualifying with a 1:55.88 but remains the favorite for gold in the event, having swum by far the fastest time in the world this year, a 1:53.09 at Australia’s Olympic trials. Because of their order of finish, Ledecky and Titmus will be in opposite heats of the semis on Tuesday. They are also expected to face off in the 800 free and the 4x200 free relay later in the meet.

Veteran Allison Schmitt, a Team USA captain swimming in her fourth Olympics, qualified in 12th place overall in the 200 free with a time of 1:57.10.

Monday was the busiest day of Ledecky’s Olympics meet, featuring 2,100 meters of racing stretched across two sessions. It was also the most meters any female swimmer has ever pulled off in a single day at the Olympics — if only because the 1,500 was not added to the women’s program until these Games.

One other swimmer at these Olympics performed the same triple duty as Ledecky on Monday: China’s Li Bingjie. But her attempt did not go as well. After winning the bronze medal Monday morning behind Titmus and Ledecky in the 400 free, Li came back in the evening and failed to advance in the 200 or 1,500, finishing 20th in the former and 10th in the latter.

Li, in other words, is human. Ledecky is something else entirely.

To keep her schedule straight in Tokyo, Ledecky typed the whole thing up ahead of the Olympics, including a rough outline of when she needed to be at the pool each morning and night and when she needed to rest.

“It’s something you don’t want to have to think about at the last minute,” she said.

Her last swim of a grueling Monday came in the final heat of the 1,500 free, a race she has long dominated, holding the top 11 times in history entering the Olympics — most of them posted at world championships and various pro meets. Naturally, she notched the top qualifying time out of the five heats, a 15:35.35 that gives her Lane 4 in Wednesday’s final. Because this is the first Summer Games to feature the women’s 1,500, it was also an Olympic record.

“None of it felt extraordinary,” Ledecky said later of her 1,500. “But I knew even as I was swimming it that the time was going to be good, just because I’m swimming well. I’m in a good spot. My stroke feels good.”

Ledecky touched the wall at 9:25 p.m. Tokyo time and climbed out of the pool for the last time, her day finally finished — well, other than the mixed zone, the warm-down and another bus ride. In other words, miles to go before she slept.