Question 1 of 51

An empty tank is filled with water from a tap at constant rate. At 10:00am the tank is $\frac{1}{2}$ full. At 11:00am the tank is$\frac{2}{3}$ full. How many hours does it tank for the tank to be filled to the brim with water?

A
6h
B
8h
C
12h
D
15h
E
None of the above