Carcass wrote:
A bag is filled with black and red marbles so that the ratio of the number of black marbles to the number of red marbles is 3 to 7. Which of the following could be the number of marbles in the bag?
Indicate all such values.
A. 20
B. 23
C. 25
D. 27
E. 30
F. 33
G. 35
H. 37
Source: 320 GRE Math Questions
If a bag contains black marbles and red marbles to the ratio of 3 to 7.
Number of marbles should be an integer value. Therefore, the least number of total marbles should be 3 + 7 = 10.
Other total number of marbles should be a multiple of 10.
Only option A and E are possible and hence the correct answers.