Swim
Pim and Bert go swimming in a river. They are good swimmers; their swimming speed is twice the speed of the river’s current. Pim starts 120 meters upstream from Bert. They swim toward each other. When they meet, they tag each other and return to their starting points. Once back, they turn around again, and continue this process — swimming toward each other, tagging, returning — until they both arrive at their own starting point at the same time.
Challenger
There may have been moments when they were swimming in the same direction. If you think not, give 0 as your answer. If you think yes, give the total distance they swam in the same direction. Round your answer to the nearest whole meter.
Mastermind
Jonneke joins in. She swims at the same speed as Pim and Bert. The two boys start again at their original positions; Jonneke starts exactly in the middle. She first swims toward Pim. When she meets him, she tags him and turns around toward Bert. When she meets Bert, she tags him and turns back toward Pim. And so on.
Pim turns around each time he tags Jonneke, and also each time he reaches his starting point. Bert does the same. They continue this process until either all three are at the same point, or all three are simultaneously back at their own starting points — whichever happens first.
There may have been moments when all three were swimming in the same direction. If you think not, give 0 as your answer. If you think yes, give the total distance they swam in the same direction. Round your answer to the nearest whole meter.