All posts by mathconfidence

December 2014 Brain Teaser Solution

Q: Tree A and tree B both have some birds.   The tree A birds tell the tree B birds “if one of you comes to our tree, our population will be the double of yours.”   The tree B birds tell the tree A birds “if one of you comes here, then our population will be equal to that of yours.” How many birds in each tree?

A:  Tree A has 7 birds and tree B has 5 birds

This can be done with guess and check or algebra

This is for statement 1)  A + 1 = 2(B – 1)

This is for statement 2)  A – 1 = B + 1

This is A in terms of B from 2) A = B + 2

Then sub into statement 1 and solve for B

B + 2 + 1 = 2B – 2

B + 3 = 2B – 2

B = 5

then can solve for A using either equation A – 1 = 5 + 1    therefore A = 7

Fuzzy Errors: Attention to Detail


Yikes!!! She saw that superscripted exponent as just a plain vanilla x.  How often do students not answer the exact question but something super wicked close?  Scores do not always reflect student knowledge and skills due to these “fuzzy errors”.

People can improve their Math skills and scores by paying attention to the details to reduce fuzzy errors.  I learned this the hard way in engineering school: a little m means milli or thousandth .001 buta big M means mega or million so if you write a M when you mean m your answer is off by a billionfold — that’s a BIG fuzzy error!

For lesson planning, multiple choice with “good wrong answers” can be used for instruction so that students see common errors and misunderstandings and get less fuzzy.  Quantitative Comparison questions are amazing for this — they were sadly deleted from the SAT in 2005 but still alive on the GRE QC questions.

During exams, I walk around with a crayon or highlighter and make visual comments on student papers to point out details such as a missed negative sign (I obviously missed the above during the College Algebra final!!).  This helps students to improve their metacognition and attention to detail which strengthens student skills, scores, confidence and enjoyment of Math.

How do you stack up?


Above are the class averages for 3 9th grade Algebra classes.

When you get back a Math test test your score isn’t that important.  What’s more important is how you did compared to the rest of the class.   If you got a 90 and the class average is 70 you rock! If you got a 90 and the average is 95 not so much!