Sunday, October 11, 2015

497: Factor Grids

Source: #mathsTLP

496: Determining the Determinant

How many different solutions can we find?

495: Pythagorean anti-Triples?

Ask your class if there are any Pythagorean anti-Triples: $\dfrac{1}{a^2} + \dfrac{1}{b^2} = \dfrac{1}{c^2}$ ?

If a, b, c are integers, the question seems harder, since 1/3, 1/4, 1/5 would be (to me) obvious answers - leading to the rules for Pythagorean triples and just using their reciprocals.


Saturday, October 10, 2015

494: NetFlix Optimization

An article about the Netflix price hike:

Netflix upped the rate of its “two-screen” plan from $8.99 to $9.99. This plan lets you watch two HD (or regular) streams simultaneously on different devices.  Netflix’s “one-screen” and “four-screen” plans remained unaffected.
Here's the thinking: If Netflix subscribers start dropping from the two-screen plans to one-screen plans, this will make them a lot less likely to share their password. No one wants a little offhand altruism to actually affect their viewing habits. That would be bad. If the resulting lack of password-sharers pushes more people to subscribe, then its worth the dollar per subscriber Netflix loses when a user downgrades because of the price increase.
Find the NetFlix subscription numbers to see how the price hike changed things. Was this a good move?

Tuesday, September 29, 2015

493: It Sure Would Be Easier

If we are told that we have a quadrilateral inscribed in a circle with diameter 10, do we KNOW if the angle at B and the angle at D are 90°? Because that sure would make it easier to find x.

Sunday, September 27, 2015

Sunday, September 13, 2015

491: Discuss the Errors, part 2

This question is from the NY Regents test, and discussed by Patrick Honner in his long-running series, "Are These Tests Any Good?".

Can your students find what is wrong with it?
How would they fix it?