Girls in Math at Yale 2022 Problem 6: in which Carissa doesn't get hit by a car
Source:
February 27, 2022
Yalecollege
Problem Statement
Carissa is crossing a very, very, very wide street, and did not properly check both ways before doing so. (Don't be like Carissa!) She initially begins walking at feet per second. Suddenly, she hears a car approaching, and begins running, eventually making it safely to the other side, half a minute after she began crossing. Given that Carissa always runs times as fast as she walks and that she spent times as much time running as she did walking, and given that the street is feet wide, find Carissa's running speed, in feet per second.Proposed by Andrew Wu