764 School Science and Mathematics

Furthermore, since positive real numbers are generally representedby numerals using base 10, the results in Theorem 3 also allow thestudent to find the characteristic of a positive real number by merelynoting the position of the decimal point in the number. Thus, thisprocedure of explaining the terms, mantissa and characteristic, allowsthe student to have not only a basis for understanding, but also amethod for finding them; and probably more important, the studentnow has an explicit mathematical reason as to why the method works.

REFERENCEREAD, CECIL B. "Do Your Students Know What a Mantissa Is? SCHOOL SCIENCEAND MATHEMATICS, LXVI (November 1966) 703-704.

Take a Coffee Break

Patrick J. BoylePiedmont Hills High School, San Jose, California 95132

Students and teachers alike look forward to "something differ-ent/7 We all need a break in the routine in order to persereve in thewild whirl of school. Here is something for your next coffee break.If you find the results worthwhile, you might use it with your thirdor fourth year students. Pm sure they will find some of the equationswith their built-in restrictions quite challenging for simple conies.Graph the following on a single set of coordinate axes. It may be

helpful to mark off ten units in each direction along the axes beforebeginning. Lots of luck!

x2 + 4:y2 - lOx - 2Sy + 65 = 0

16x2 + WOy2 - 160^ - 700:y == - 1525

4x2 + 4:y2 - ^y + 21 > 0

-3(y - .8) == V14.76 - 14.4;y - x2

(9x2 + 100:y2 - 1100y + 2800 < 0

[9x2 + 64:y2 - S12y + 880 <, 0

Wx2 + S76y2 = 3136

^ + 49^2 ^ 195

[4x2 + 4y2 - 44;y + 21 > 0

(^ + 4^2 - 44^ + 21 = 0

1[ y - 3.15 | - 2.35 < 0

l.Ox2 + ll.ly2 - 122.2y + 311.1 <, 0

(See p. 772 for correct response)