timon 2

What’s the relationship between division and square roots in students’ minds? Why did the kid write 15 / 15.

[Note: no idea how to categorize this in CCSS. Also, thanks to Timon for the submission.]

  • Ines

    Is this the logic? 15^2 = 15*15 so sqrt(15) = 15/15. But why doesn’t the answer = 1?

  • This student seems to understand the concept of a square root, as evidenced by the approx. of 3.9 being a little less than 4, which would’ve been sqrt(16). Seems as if he’s trying to show the opposite of repeated mult., which we’ve seen as a go to for students when they’re considering exponents. Maybe he’s having difficulty with going from the abstraction of the concept in his head to the concrete numerical expression on paper?

  • Approximating square roots is an 8th Grade standard — 8.NS.2: Use rational approximations of irrational numbers to compare the size of irrational numbers, locate them approximately on a number line diagram, and estimate the value of expressions (e.g. pi squared).

  • It could be that the student got caught in the long division vs square root debacle.

  • AMoore

    I agree with Ines. However the answer probably doesn’t equal 1 because the student probably used a calculator and put in sqrt (15) instead of 15/15.