Mr. Richard plans to take 25 students on a school trip. They plan to go to Zoo. The bus fee is $100 for the entire trip. Entrance fee is $2.50 per person. How much should each student pay? Note: Mr. Richard does not need to pay.

Here is their argument. given the obtuse angle x, we make a quadrilateral abcd with ∠dab = x, and ∠abc = 90◦, and ad = bc. say the perpendicular bisector to dc meets the perpendicular bisector to ab at p. then pa = pb and pc = pd. so the triangles pad and pbc have equal sides and are congruent. thus ∠pad = ∠pbc. but pab is isosceles, hence ∠pab = ∠pba. subtracting, gives x = ∠pad−∠pab = ∠pbc −∠pba = 90◦. this is a preposterous conclusion – just where is the mistake in the "proof" and why does the argument break down there?

For an experiment, a penny is tossed. at the same time, a spinner with 8 congruent sections numbered 1–8 is spun. how many possible outcomes are there for the experiment?

In need of in the diagram, ∠abc is a right angle. ∠dbc = 30°27'40". find the measure of ∠abd.