Off on a Tangent
A Fortnightly Electronic Newsletter from the Hope College Department of Mathematics
 March 2, 2018 Vol. 16, No. 11

Upcoming Colloquia

The  following colloquia are on the schedule for this semester. Additional ones may be added later.
  • Tuesday, April 3, Ed Aboufadel, Grand Valley State University
  • Tuesday, April 17, Yew Meng Koh, Hope College
  • Thursday, April 26, Martha Precup, Northwestern University

Math Department Spring Social

Come eat pizza and play games with your fellow math students and the math department on Thursday, March 8! 

We will meet in VZN 298/299 (one room with be used for games and the other for pizza). The event starts at 6:28 pm (that is 2pi or tau o'clock) and ends at 9:42 pm (I'll let you figure out the significance of this time). Sign up in your math class. It will be more fun than a barrel of monkeys!

Professor Cinzori has a fairly large selection of games. He has them listed here. Let him know if you have a particular game you would like him to bring.

Lower Michigan Mathematics Competition

The 42nd Annual Lower Michigan Mathematics Competition (LMMC) will be held at Hillsdale College this year on Saturday, April 7.  Students from colleges and universities in Michigan will gather to challenge themselves on ten interesting problems, working together in teams of up to three people. The competition takes place in the morning and after lunch there is a discussion of the solutions. 

If you want to participate, please sign up by Wednesday, March 14 (right before spring break) by sending Prof. Cinzori's an email at  You may register as a team (of two or three) or individually (and you will be placed on a team).

The picture shown with Hope Students holding the Klein Bottle Trophy for winning the LMMC is getting a bit old. It would be nice to have a victorious team so this picture could be updated!  For more information and links to old tests click here.

Problem Solvers of the Fortnight

In our last problem of the fortnight we had the following:

Four circles are tangent to each other and tangent to two nonparallel lines, as shown in the figure.  The radius of the smallest circle is 4 and the radius of the largest circle is 9.  Find the radii of the other two circles.

Congratulations to Grace Ahlgrim, Annie Dankovich, Philip LaPorte, Zheng Qu, Forest Rulison, Yizhe Zhang, and Will Zywicki for submitting correct solutions.

Problem of the Fortnight

A teacher chose a 5 digit number and asked her ten students to try to guess the number she chose. Nobody succeeded, but each student did get one, and only one, of the five digits correct in the right position. The student guesses were 

06432, 29751, 94700, 38977, 87036, 43069, 76330, 52025, 61825, 18641

What is the teacher's number?.

Write your solution (showing all relevant work) and drop it in the Problem of the Fortnight slot outside Professor Mark Pearson's office (VWF 212) by 3:00 p.m. on Friday, March 9.  As always, be sure to include your name and the name(s) of your math professor(s) -- e.g. Moe Mentum, Professor Sara Bellum  --- on your solution.

Pure mathematics is the world's best game.  It is more absorbing than chess, more of a gamble than poker, and lasts longer than Monopoly.  It's free.  It can be played anywhere - Archimedes did it in a bathtub. 

~Richard J. Trudeau, Dots and Lines

Off on a Tangent