The conditional in this problem (i.e.) "if no flowers are to be left out" is the key to solving; you should interpret this conditional statement as "I need to find the

Greatest common divisor among Red and White Tulips.

1. Red Tulips = 91 ; White Tulips = 21

2. To find the Greatest Common Divisor, the quickest method is prime factorization.

3. So, with prime factorization,

red tulips = 91 = 7 x 13.

White tulips = 21 = 3 x 7. 4. The divisor common in both (7 x 13) and (3 x 7) is

7.

Therefore, the answer to this problem is (E) 7This problem is on both the 2013 and 2017 GMAT

OG.