It will take 1/2 an hour because if 1/2 of a wall is painted with 1/4 of an hour, then we know if you want the other half, you have to add another 1/4 of an hour which is 2/4.
2/4 is equivalent to 1/2 so 1\2 of an hour is how long it will take.
Countinue to learn and grow! ☆