Solution: We are given:
The first week, Bean sprout grows 3 inches
The second week, Bean sprout grows 2 inches
The third week, Bean sprout grows 1.333... inches
Bean sprout follows a particular each week. Every week it grew 2/3 (0.667) less than the week before.
For the first week it was 3 inches, for the second week it was
inches, for the third week it was
and therefore, for the fourth week it will be

Therefore, bean sprout have grown 0.8889 inches in its fourth week.