Prep Math question

ds-1 problem 10

10.        719-!-item-!-187;#058&000515

Of the 800 students at a certain college, 250 students live on campus and are more than 20 years old.  How many of the

800 students live on campus and are 20 years old or less?

(1)  640 students at the college are more than 20 years old.

(2)  60 students at the college are 20 years old or less and live off campus.

The answer is C, but I feel it is B

ds-1 34

During an experiment, some water was removed from each of 6 water tanks.  If the standard deviation of the volumes of water in the tanks at the beginning of the experiment was 10 gallons, what was the standard deviation of the volumes of water in the tanks at the end of the experiment?

(1) For each tank, 30 percent of the volume of water that was in the tank at the beginning of the experiment was removed during the experiment.

(2) The average (arithmetic mean) volume of water in the tanks at the end of the experiment was 63 gallons.

The answer is A, I feel is D.

Thank you