SAT Mathematics Practice Test 3

Let x be the number of left-handed female students and let y be the number of left-handed male students.
Then the number of right handed female students will be 5x
and the number of right-handed male students will be 9y.
Since the total number of left-handed students is 18 and the total number of right-handed students is 122,
the system of equations below must be satisfied.
{

x+y=18

5x+9y=122

Solving this system gives x = 10 and y=8.
Thus, 50 of the 122 right-handed students are female.
Therefore, the probability that a right-handed student selected at random is female is

50

122

, which to the nearest thousandth is 0.410.
Choices B, C, and D are incorrect and may be the result of incorrect calculation of the missing values in the table.