Two Coins   Suppose a country only issued two types of coins to be used as currency: one 7 unit coin and one 11 unit coin.  This would cause a dilema since certain prices could not be paid exactly, such as 13 units.  If this was the case, what would be the greatest price that could not be paid with any combination of the two coins?
February 13, 2006
Past Problems
	E-mail Solutions to: pow@umassd.edu
	Correct Solutions
	Radu Ionescu. Montreal, Quebec, Canada Teruo Goto. Aichi, Japan Frank McGartland. Saskatoon, SK., Canada Sagar Patel. Brookstone School, Columbus, GA Derek Brown. Forsyth Country Day School, NC Marius Damian. Braila, Romania David Madfes. San Francisco, CA Adrian Atanasiu. Bucharest, Romania Emil Lalov. Mathematical High School, Pleven, Bulgaria Skyler Weaver. Oregon State University, Corvallis, OR Tim Poe. Austin, TX Hendrik Salomons. Montana Farm, Brazil Ken Tyburski. Chatham Hall Mathematics Faculty, Chatham, VA Wenlin Fan. Mountain Top, PA Arjun Vijayakumar. Bridgewater-Raritan Middle School, Bridgewater, NJ Lisa Schechner. Schreiber HS, Port Washington, NY Gary Brensike. Fairfax, VA Phillip Ai.  Hammarskjold Middle School, East Brunswick, NJ Bob Mitchell. Normal, IL Russell Beaty. Brookstone School, Columbus, GA David Shi. JLS Middle School, Palo Alto, CA Brittany Cole. Dartmouth High School, Dartmouth, MA Matthew DeCoste. La Canada Middle School, La Canada, CA Sahana Vasudevan. Vargas Elementary School, Sunnyvale, CA Roland Vyncke. Brugge, Belgium Greg LaCroix. Somerdale, NJ Bar Greengrass. Israel Thomas Robertson. Riverside, RI Tom Lindsay. Carver, MA Mark Spanier. Sauk Centre HS, Sauk Centre, MN Timothy Yales. Westland, MI Daniel Senécal. Montréal, QC, Canada Jerome Cherry. Mundare, Alberta, Canada Aristides Kyriakakis.  Thessaloniki.  Greece Mary Wickham. Brookstone School, Columbus, GA Tiffany Chen. South Pasadena Middle School, South Pasadena, CA Aashrita Mangu. South Pasadena Middle School, South Pasadena, CA Alexandr Wang. Pinon Elementary School, Los Alamos, NM Serena Kulmatyski. R.F. Staples, Westlock,AB Rin Sone. South Pasadena Middle School, CA Michelle Lam. South Pasadena Middle School, South Pasadena, CA Soo-Yung Lee. Sauk Centre HS, Sauk Centre, MN Brianna Loo, South Pasadena Middle School, South Pasadena CA Farid Lian, Uniatlantico, Barranquilla, Atl. Kunal Singh. Kendriya Vidyalaya, Happy Valley, Shillong, India Nick Taylor. US Air Force Academy, Colorado Springs, CO Alexander McAvoy. Amanda Tu. Southridge School, Surrey, BC, Canada Joe Brophy. Boston, MA. Ben Gieske. Sauk Centre HS, Sauk Centre, MN Michael Vishevnik. Levittown, PA Brian Hetrick. UNH, Durham, NH Katherine Wang.  South Pasadena Middle School, South Pasadena, CA Daniel Pyon. South Pasadena Middle School, South Pasadena, CA Max White. South Pasadena Middle School, South Pasadena, CA Dennis Gorshteyn. South Pasadena Middle School, South Pasadena, CA Verònica Expósito. Argentina Ted Aronson.  Norwood, MA Svadharma Keerthi. South Pasadena Middle School, CA Daniel Acosta-Kane. Miami Killian Senior High School, Miami, FL
	32% of respondents successfully answered this problem.

 

 Last Updated On: 2/21/06