The task is to generate the correct answer for a given math problem.

Problem: an aeroplane covers a certain distance of 670 kmph in 6 hours . to cover the same distance in 6 1 / 4 hours , it must travel at a speed of
643

Problem: in one alloy there is 12 % chromium while in another alloy it is 8 % . 35 kg of the first alloy was melted together with 40 kg of the second one to form a third alloy . find the percentage of chromium in the new alloy .
9.75 %

Problem: the ratio of the volumes of two cubes is 125 : 512 . what is the ratio of their total surface areas ?

25 : 64