Charla wants to cover a certain rectangular area of her driveway with a picture using chalk. If she completes 2/3 of the area in 1/2 hour how long will it take her to complete the entire picture
If Charla completes 2/3 of the area in 1/2 hour, then 1/3 of the area is left to complete.
Since 2/3 of the area is completed in 1/2 hour, then 1/3 of the area is completed in 1/2 * (1/2/3) = 1/2 * 2/3 = 1/3 hour.
Thus, it will take Charla 1/3 hour to complete the entire picture. Answer: \boxed{\frac{1}{3}} hour.