Correct Guess

My two daughters recently entered a contest at our local library to win a set of kids magazines geared toward their age.  To win the set of magazines, they had to guess how many Legos were in a jar.  The entry with the closest guess wins the prize.  Some people may claim we cheated, but I disagree.  We simply used math skills to help us out.  I began by letting them know there was a method that would help us with our guess.  I told them that if we know how many Legos tall the jar is and how many Legos across the jar is, we could do a bit of math to get a close guess.  Here's how:

The jar was cylindrical and there's an equation for the volume of a cylinder.  The volume of a cylinder is given by:

V = Base Area*Height = pi*r^2*h

I told them to count the number of Legos high, and they each did.  Then I asked them to count the number of Legos across (diameter) and they both did.  We plugged the numbers in a calculator and they both had a number they wrote down and put in the guess box.  A week later after the contest had ended, I received a phone call letting me know that my 4 year old had the closest guess!  She was only 1 Lego off!!!

So who said knowing math doesn't come with perks?  Okay, perks for my 4 year old, but perks nonetheless!