Wednesday, April 23, 2008

Math problems of the week: linear equations in reform vs. traditional algebra

1. From "Say it with Symbols," Investigation 4, about 2/3 of the way through the 8th grade Connected Mathematics curriculum:

The school choir is selling boxes of greeting cards to raise money for a trip.  The equation for the profit in dollars, P, in terms of the number of boxes sold, x, is
P = 3x - (100 + 2x).

a. How many boxes must the choir sell to make a $200 profit?  Explain how you found your answer.
b. How many boxes must the choir sell to break even?  Explain how you found your answer.


2. From "Systems of Linear Equations and Inequalities," about 2/3 of the way through McDougal and Littel's Algebra 1, a traditional text:

A gold and copper bracelet weighs 238 grams.  The volume of the bracelet is 15 cubic centimeters.  Gold weighs 19.3 grams per cubic centimeter, and copper weighs 9 grams per cubic centimeter.  How many grams of copper are mixed with gold?


OILF's assessment:

Translating a word problem into an equation is a core skill, and challenge, in algebra.  

The main problem with Connected Math is how easy it is.  In particular, rarely does it ask students to translate word problems into equations without guiding them through key steps.

If a problem is hard enough that students can't do it in their heads, then you don't need to ask them to explain how they found their answers.

1 comment:

november said...

this is great post...
nice blog