Tag Archives: Conversions


It’s safe to say that thunderstorm season has officially arrived in Iowa!  The temperature and the humidity has been on a steady climb for the last couple of weeks (remember when we were making jokes about how cold it was?!?) and seasoned midwesterners can spot the ideal weather for a good thunderstorm from miles away!

I love thunderstorms!  For some reason, they always prompt me to bake a batch of chocolate chips cookies whenever they roll through!  (There’s nothing quite like watching the clouds roll in while you chow down on homemade cookie dough!)  Unfortunately, my children do not share my affinity for thunderstorms, not even the promise of warm chocolate chip cookies can calm their nerves when the thunder starts booming and the lightening flashes!

Last week a quick thunderstorm rolled up in the middle of dinner.  Instead of focusing on the scary booms and flashes I said to them “Did you know if you count the number of seconds between when you see the lightening and hear the thunder, you can estimate the distance the thunderstorm is from our house?”  (P.S. Did you know that?)

The speed of sound through the air is approximately 340 meters per second, and the speed of light is approximately 300 million meters per second.  Even though thunder claps and lightening  flashes are happening at the same time, the difference in speed makes it seem as though the lightening is flashing before the thunder.

Using the relationship between distance, rate, and time we know that D = R*t, where D is distance, R is rate, and t is time.  Since we have the rate of sound and light in meters and seconds, we’ll also report D and t in terms of meters and seconds.

Now, suppose you hear thunder approximately 5 seconds after you see a flash of lightening.  If we use the relationship between distance, rate, and time we can substitute known values into the equation, which gives us D = 340*5 = 1700 (remember this is meters).  1700 meters is approximately 1 mile.

The next time a thunderstorm rolls up in your neighborhood, see if you can track how quickly its  moving through the area.  Keep a record of the length of time between lightening flashes and thunder rumbles.  Can you tell when the storm is getting closer and farther away from you?

P.S. I got my facts and figures from two great sources: the National Weather Service and The Department of Physics at the University of Illinois Urbana Champaign.




Screen time

It’s been a while since I’ve written about a mathematics problem from NCTM and I kinda of miss writing about them (You can read the other ones here and here)!  Last week they posted a question that only got snarky answers on Facebook, so I decided this would be the perfect one to write about 🙂

Here’s the post:

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From the snarky answers it seems to have drawn criticism because of the number of movies Ryan supposedly has, but I just have to say from my own experience that my children could certainly given Ryan a run for his money in the movie collection department!

Anyway, Ryan’s movie collection is apparently quite extensive.  Also, he only likes movies that are fairly short (1 hour and 30 minutes in total).  If Ryan were to watch these movies back to back to back to back to (you get it, all 70 without stopping); how many days would it take him to watch said movies?

Can you tell right off the bat that this is a conversion situation?

My game plan:

Convert hours and minutes to the same unit of measure; then use this unit of measure to calculate the number of days of the marathon movie watching!

Except that as I was typing this, I came up with another game plan . . . each pair of movies equals 3 hours.  Then, I don’t have to worry about converting minutes to hours or hours to minutes.  AND, 70 is an even number of movies, meaning I can make pairs of movies without leaving any movies out.  AND, 3 hours is a really nice value to have when dealing with days, because there are 24 hours in a day and 3 divides 24 evenly.  So, I can watch 8 pairs of movies a day (or 16 movies a day).

New Game Plan:

16 goes in to 70 little more than 4 times (actually it goes into 70, 4.375 times)

That means Ryan will need to watch 8 pairs of movies for 4 days.  At the end of 4 days he will have watched 64 movies, leaving him the final 6 movies (or 3 pairs of movies, or 9 hours of movies) for the 5th day.

So my final answer is 4 days and 9 hours of movies to watch all 70 movies!

Just to double check, you could do the converting I described at the beginning of the post . . .OR you could describe a different method to do the calculations if the mood strikes you!  If you do this another way, I’d love to hear about it in the comments below!

I also feel the need to address the posts on Facebook about Ryan’s movie situation.  Most of the comments were along the lines of “only a mathematics website, textbook, teacher, etc., etc. would ask such a silly question.  This question isn’t realistic.”  I must say I have to respectfully disagree.  The first thing I thought about when I read this question was the Brita water filter commercial showing plastic water bottles stretched across the Earth’s surface.

If this commercial had been written as a word problem in a mathematics class, it probably would have sounded a little something like this:

The makers of Brita water filters claim that 1 filter is able to filter the equivalent of 300, 16.9 oz. bottles of water.  Suppose Ryan uses 1 Brita water filter per month for one year.  If Ryan had used plastic bottles, instead of water filters how many times could the number of plastic bottles used wrap around the equator of the Earth?

I’m willing to admit that this type of problem situation isn’t one that we encounter in our every day lives; however these types of conversion situations come up whether they be for impact, or marketing, or something else.  Isn’t nice to know that you . . . reader of the It’s Just Math Blog have a way to evaluate such statements for their accuracy?

And finally, with regard to Ryan and his movie watching I’m willing to bet that the following problem statement may have been a little more well-received.  Why?  You might ask?  Because most of us know someone who’s done this 🙂  If this problem statement had been written about me it would have been about watching Law and Order SVU marathons 🙂

Suppose Ryan is a huge fan of James Bond movies.  In fact, this weekend he plans to watch every James Bond movie ever made back-to-back.  Will he have enough time to watch all of the movies if he starts Saturday morning at midnight and finishes Monday morning in time for school at 8am?

Iowa Butter Cow

I’ve lived in Iowa for 27 of my 32 years, but until 2 days ago I had never been to the Iowa State Fair.  It’s true what they say, you can get everything on a stick and the fair is larger then anyone could imagine (well, until you’ve been there of course!)


(My children watching some sort of cow show.  You can tell the 2-year was enthralled; the other   2 were humoring their little sister)

The Iowa State Fair frequently shows up on National and Families with Kids Summer Bucket Lists.  In fact, this year Al Roker visited the fair!

One of the main attractions at the fair is the Butter Cow.  Its a sculpture of a cow made entirely of Iowa Sweet Cream Butter (with a little help from wood and wire forms underneath it all!).

I’d heard about the Butter Cow before.  I’m sure I’d even seen a picture or two of the cow, but as soon as we got through the gates and on to the fair grounds I told my family the first thing we must see is the Butter Cow!  So my family of 7 (my mom and dad were with us, also visiting the Iowa State Fair for the first time) walked right past the bacon wrapped ribs on the stick, and the hand-dipped corn dogs (OK, OK so we made an impromtu stop at the mini cinnamon roll stand . . . you would understand, if you could have smelled them) to see the famous Butter Cow.

We could tell where the cow was, before we even saw it because of the steady stream of people walking by the large window to catch a glimpse of the cow.  But, when we finally got there this is what we saw:


Pretty impressive, if you think about it.  The butter cow is about 5 feet 6 inches tall and 8 feet long.  It weighs approximately 600 pounds (a really dairy cow weighs about 1000 pounds)  According to the Iowa State Fair website the butter cow could butter about 19,200 slices of toast and would take the average person 2 lifetimes to eat.  These statistics got me thinking:

1. If this cow could butter 19,200 pieces of toast, how much butter is being put on each piece of toast?

2. If it would take the average person 2 lifetimes to eat the butter cow, how much butter per day is the “average person” eating?  And, what makes a person “average”?

3. In the video about the 2013 butter cow artist Sarah Pratt says that this year’s cow weighs between 450 and 50 pounds.  If one stick of butter weighs 4 ounces, approximately how many sticks of butter were used for this year’s butter cow?

Want to know more about the Butter Cow?  Check out this YouTube video produced by Iowa Public Television.

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