Imagine Chris swimming in a river, 50m from the bank.
She is enjoying her swim when she notices her husband, who is looking after the family 100m along the river bank, calling her for lunch.


She'd like to get back to her family as quickly as possible. If she can swim at 3 m/sec and run at 7m/sec, how far along the bank should she land in order to get back as quickly as possible?