The national average for mathematics on a standardized test in 2011 was 526. Suppose that the distribution of scores was approximately bell-shaped and that the standard deviation was approximately 47. Within what boundaries would you expect 95% of the scores to fall?

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?

Is trapezoid abdc the result of a dilation of trapezoid mnpq by a scale factor of ? why or why not? yes, because ab and cd are each the lengths mn and qp. yes, because sides ab and cd are parallel to sides mn and qp. no, because ab is the length mn but cd is the length qp. no, because sides ab and cd have different slopes from sides mn and qp.

Which of the following is the best first step in solving the equation below? 4+2㏒³x=17