Trivia Why's by Trivia Why's Guy

A1) Subtrahend. The original number is the minuend, and the result is called the difference.
A2) 4. A composite number is roughly the opposite of a prime number (every non-prime greater than 1 is a composite).
A3) Multiplication. The technique involves drawing a lattice (grid) with one factor across the top and the other down the side. Each product of two single digits goes into a cell split diagonally for the tens place and the ones place. Summing along the diagonals produces your final product. (Sorry, that was pretty hard to follow; here's a better explanation of the Lattice Method with pictures.)
A4) Reflex. An angle between 0 and 90 degrees is acute, 90 degrees is right, and between 90 and 180 is obtuse.
A5) Trapezoid. If two pairs of sides are parallel, you have a parallelogram. If two pairs of sides are of equal length but no sides are parallel, you have a kite. Oddly, there is no special term for a figure with four unequal sides and four unequal angles (roughly equivalent to a scalene triangle).
A6) Parabola. It is also the curve formed by the intersection of the surface of a cone and a plane parallel to one side of the cone.
A7) 540 degrees. The angles in a triangle add to 180 degrees, a quadrilateral to 360, and so on. If N is the number of sides in the polygon, the interior angles add up to 180(N-2).
A8) 16 cubic units. The volume is calculated as one-third of the area of the base times the height. Surprisingly, the shape of the base and the number of sides on the pyramid are irrelevant.
A9) 43,560. The funny number comes from an estimate of how much one yoke of oxen could plow in one day, multiplying a breadth of one chain (or four rods, or 66 feet) by one furlong (660 feet). An acre would cover an NFL football field from the back of one endzone to the opposite 20-yard line (or, if you prefer, from one 5-yard line to the other 5-yard line [plus another three-fourths of a yard to be exact]).
A10) 128. There are 8 fluid ounces in a cup, 2 cups in a pint, 2 pints in a quart, and 4 quarts in a gallon. And to complete the sequence on the small side, 2 tablespoons equal an ounce, and 3 teaspoons equal a tablespoon. Add a pinch or a dash at your discretion.
A11) 1 kilogram. By contrast, a gallon of water weighs 8.345 pounds (a quart equals 2.086 pounds), which is as round as your browser window.
A12) The order of operations in calculations. The first letters PEMDAS stand for Parentheses, Exponentiation, Multiplication and Division, and Addition and Subtraction.