Acone has a height of 24 inches, a slant height of 25 inches, and a diameter of 14 inches. what is the surface area of the cone?

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.

its 4 because 2 times 2 is 4, if you double the number two you get four