Li Na is going to plant 63 tomato plants and 81 soy bean%C2%A0plants. Li Na would like to plant the plants in rows where each row has the same number of tomato plants and each row has the same number of soy bean plants. What is the greatest number of rows Li Na can plant?
To find the greatest number of rows Li Na can plant, we need to find the greatest common divisor (GCD) of the number of tomato plants (63) and the number of soy bean plants (81).
The prime factorization of 63 is 3 * 3 * 7.
The prime factorization of 81 is 3 * 3 * 3 * 3.
Therefore, the GCD of 63 and 81 is 3 * 3 = 9.
Since each row must have the same number of tomato plants and soy bean plants, the greatest number of rows is equal to the GCD, which is 9.
Therefore, Li Na can plant the plants in 9 rows. Answer: \boxed{9}.