Chapter 1.1, Problem 43E

DISTANCE BETWEEN TWO CARGO SHIPS Sailing north at a speed of $25\text{mph}$, Ship A leaves a port. A half hour later, Ship B leaves the same port, sailing east at a speed of $20\text{mph}$. Let $t$ (in hours) denote the time Ship B has been at sea.
a.	Find an expression in terms of the time t that gives the distance between the two cargo ships.
b.	Use the expression obtained in part (a) to find the distance between the two cargo ships $2\text{hr}$ after Ship A has left the port.