Answer:
a) 15-t mph;
b) 15+t mph.
Step-by-step explanation:
a) When the boat travels upstream, the current hinders the boat (the speed of the boat decreases). Thus, the speed of the boat upstream becomes
15-t mph.
b) When the boat travels downstream, the current helps the boat (the speed of the boat increases). Thus, the speed of the boat downstream becomes
15+t mph.
3ft
