Abean sprout grows 3 inches in its first week, 2 inches in its second week, and 1.333 inches in its third week. if the sprout's growth follows this pattern how much will the bean sprout have grown in its fourth week.

If the sprout's gorth follows this pattern, it will continue to decrease in growth by 2/3 each week.
First Week: 3in                 3 x  = 2
Second Week: 2in            2 x  = 1.333
Third Week: 1.333in          1.333 x  = 0.889
Fourth Week: 0.889in

I’m not sure how this works