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Peak numbers

Published online by Cambridge University Press:  01 August 2016

Tabitha T. Y. Mingus  and
Richard Grassl
Tabitha T. Y. Mingus
Affiliation:
Department of Mathematics and Statistics, Western Michigan University, Kalamazoo, MI 49008 USA
Richard Grassl
Affiliation:
Department of Mathematical Sciences, University of Northern Colorado, Greeley, CO 80639 USA
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Extract

Two recent problems appearing in die September 1997 and September 1999 issues of the NCTM publication Mathematics Teacher asked the following:

A. An integer is called decreasing if each digit is less than the one to its left. Determine the number of decreasing integers between 2000 and 7000.

B. A 5-digit integer is a peak number if its digits strictly increase to the middle one then strictly descend. Determine the number of 5-digit peak numbers that are greater than 70,000.

Type
Articles
Information
The Mathematical Gazette , Volume 86 , Issue 505 , March 2002 , pp. 44 - 50
Copyright
Copyright © The Mathematical Association 2002

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References

1. Grassl, R. The squares do fit!, Math. Gaz. 79 (July 1995) pp. 361–364.CrossRefGoogle Scholar
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4. Petkovsek, M. Wilf, H. Zeilberger, D. A = B, A. K. Peters (1996).CrossRefGoogle Scholar
5. Grassl, R. Mingus, T. Keep counting those boxes – there’s more, Mathematics Teacher 91 (February 1998) pp. 122–127.CrossRefGoogle Scholar