How many different towers can you make using one red, one blue and one yellow block?

You can make 6 different towers. If red was at the bottom, there'd be two different possibilities for that: red, yellow, blue, and red, blue, yellow. Same for if blue was at the bottom: blue, red, yellow, and blue, yellow, red. Yellow also applies: yellow, red, blue, and yellow, blue, red. 3*2=6, so 6 possible towers. 

31%.

The car bought most often by both males and females collectively is the white car.  That has a total frequency of 0.31 out of 1 or, 31/100