40. The
integers 1, 2, 3, ..., 50 are written on a chalkboard. After
erasing N
of
these 50 integers from the board, the product of the remaining
integers ends in 8. Compute the least possible N.
41.
The zeroes of f(x)
= Ax5
+ Bx4
+ Cx3
+ Dx2
+ Ex
+
F form
an arithmetic progression of positive integers whose average is
2013. For all possible values of the coefficients A,
B,
C,
D,
E,
and F,
compute the least possible zero of g(x)
= Fx5
+Ex4
+Dx3
+Cx2
+Bx+A.
42. Voyager 1 is the man-made object that is furthest from the
Earth. How long will it be before New Horizons is
further? Explain your assumptions. (Show work, do not
only quote a source.) Suppose you drive to Syracuse on the
thruway for 2 hours at 65 mph. If you make the same trip at 70
mph, how much time do you save? If you drive for an hour
through the city and average 30 mph for that time, then get on the
thruway, how long do you need to drive at 70 mph to raise your
average speed to 45 mph? Find a formula for the time it takes
to raise your average speed to a general speed s. For which
values of s is your formula valid?
43. This question feels related to me: You're taking a
class where 20% of your grade is determined by the final. You
hope to pull your grade up 2 points by the final. How much
better do you need to do on the final than you have done in the
course? Why is this much more difficult if you are trying to
earn an A than if you are trying to earn a B? As long as we're
talking about grades … some people use a 4 point scale for their
class instead of a 100 point scale. What are the mathematical
differences and how do you feel about them
pedagogically? What would be the ramifications of using
median for course average instead of mean?