Northeastern Section of the
Mathematical Association of America

2009 Collegiate Mathematics Competition

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Practice Problems for 2009

Date
Problem
Solution
Th, 10/8
For what value of $k$ does the equation $e^{2x}=k\sqrt{x}$ have exactly one solution? Solution
M, 10/12
A student forgot the Product Rule for differentiation and made the mistake of thinking that $(fg)'=f'g'$.  However, he was lucky and got the correct answer.  The function $f$ that he used was $f(x)=e^{x^2}$ and the domain of his problem was $(\frac12, \infty)$.  What was the function $g$? Solution
W, 10/14
Show separately that the numbers 10201, 10101, and 100011 are composite in any base. Solution
F, 10/16
Solve $\sqrt[3]{13x+37} - \sqrt[3]{13x-37}=\sqrt[3]{2}$. Solution
M, 10/19
Let $A$ be a square matrix of rank 1 and trace 1.  Prove that $A^2=A$. Solution
Tu, 10/20 We apologize for the technical difficulties the past few days!  We hope that all the problems caused by my math display software upgrade have been resolved!!
W, 10/21
The expression $a|b$ means that $a$ divides $b$.  Suppose that $2^{m}|(3^{m}-1)$.  Show that if $m\ne 1$, then $m$ is even. Solution
M, 10/26
A 10-foot pole is dropped into a milling saw and randomly cut into three shorter poles.  What is the probability that these three pieces will form a triangle? Solution
M, 11/2
Without performing multiplications, find the digits $a$ and $b$ in
23! = 2585201ab38884976640000.
Solution
W, 11/4
Given
f(x)=\frac{607}{607x+1} + \frac{692}{692x+1}+\frac{-701}{-701x+1}.
determine, without using a computing device, whether or not $f^{(12)}(0)=0$.
Solution
M, 11/9
A curve is defined by the parametric equations
x=\int_1^t \frac{\cos u}{u}\,du \qquad y=\int_1^t \frac{\sin u}{u}\,du
Find the length of the arc of the curve from the origin to the nearest point where there is a vertical tangent line.
Solution
W, 11/11
Find the largest possible area of a pentagon with five sides of length 1 and a right interior angle. Check back on F, 11/13