All posts by mathconfidence

August 2016 Brain Teaser Solution

Q: In the “old days”, most people wore a watch and it was not always accurate.  A friend had a watch that gained 6 minutes every hour.  If this watch is set accurately at midnight and the watch stopped a half hour ago and it now shows 8:26AM, what is the current correct time?

A: The watch is gaining 6 minutes every hour, for every hour, the watch will show 66 minutes. Since the watch shows 8:26 am, we know that 506 watch minutes have passed which is 460 real minutes (506 x 60/66 ) = 7 hrs and 40 minutes which would make it 7:40.
The watch stopped 30 minutes ago, therefore the time must now be 8:10 am.

 

 

 

Get the Math & Points June 2016 CC Alg I Regents #16

June 2016 CC Alg I 16Put j(x) into Y1 and try the other equations in Y2 then compare the Y1 and Y2 columns
Below is answers 1 and 2 which have the same equation, neither is a match!

Now we will try the equation for (3) and (4), see below:
CC Alg I June 2016 16c y

So now we can see the match!
However, at x = -6, the y value is 115 and we are looking for -29, so it cannot be -6

June 2016 Alg I 16 c check

At x = 6 below, you can see the y value is -29.
Also check out the symmetry of the y values and how the values are centered around (6,-29): this is what makes it the vertex or turning point.

June 2016 Alg I 16 table right

We could also use the vertex form of a parabola but it  has a tricky negative sign issue which these answer choices prey upon.
Using the graph feature of the  TI-84 is also an option but since the normal viewing window is +/-10,  -29 would be outside that window.