Wednesday, December 26, 2012

Exponential Pushups: How Many Can Your Students Do

The purpose of this exercise is twofold; first, to show exponential growth, second to serve as a fun way of testing your student’s knowledge of exponents.

  • Ask you classroom who can do 2 push-ups? Have someone show you.

  • Explain that this is the same as doing 2^1 pushups.

  • Ask you classroom who can do 4 push-ups? Have someone show you.

  • Explain that this is the same as doing 2^2 pushups

Continue this exercise until you get to 2^7, from here have them calculate and image doing that many pushups. Where you stop from here is up to you.

Next, pair up your students and give them a worksheet with exponent problems. The only catch is, they must show you what the answer is by doing pushups.


  • 3^2 a student from the group must show you the answer is 9 by performing 9 pushups.

Monday, December 24, 2012

Which Letters Of The Alphabet Are Graphs of Polynomials?

This light exercise is to get your students thinking about polynomial graph behavior. You could extend this exercise to guess they degrees and signs of the leading coefficients if desired. Simply print out a worksheet of all the letters of the alphabet and ask your students which letters are graphs of polynomials based on the following distinctions

  1. Polynomial graphs are continuous. You can draw them without lifting your pen
  2. Polynomial graphs have no sharp corners or cusps, they are smooth (see pic below).

See for a great tutorial and pics.

Friday, December 21, 2012

Using Word Search For Learning Key Words

Let's assume you want your students to learn all the key words for addition, subtraction, division or multiplication. Try using a word search without telling them the words to search for.

Wednesday, December 19, 2012

The Power of Actually Counting Large Numbers

One Thousand Pennies

Most four-year olds are very inquisitive. Mine loves developing his number-sense. He loves to ask me “Daddy, which is bigger ___ or ___ “as if the two numbers were about to bout, with the larger being the victor. Without ever practicing counting, he has learned to count to roughly 100 with only a few mistakes. More interesting than this is his development of number placement. Whereas many younger children can count, say to 10, ask them to count backwards and they begin to struggle. Although not fast, my son tends to count backwards just as well as forwards and I think the reason for this is that he developed his sense of numbers slowly without being asked to chant “one, two, three, four…” out loud until he remembered it. With this in mind I want to show you where counting has much more power, with large numbers.

One day my son asked me why 1000 was larger than 100. As most would, I started by telling that it takes ten 100’s to make 1,000, etc, etc. But noticing the blank look I asked for his patience as I decided to count aloud to 100 and then continued onward to 1000. His bright eyes sold me! There was no doubt after about 15 minutes later that 1000 was bigger than 100. To this day he still remembers how big it was.


How To Use This In A Classroom

For a better appreciation of larger numbers from your students have them count them.

Take 15 mins of down time and have your students listen as you count aloud to 10, than 100 than 1000.  Have them time you (you will most likely average one number per second). Next, have them calculate how long it would take to count to 10,000 or 100,000 or 1 million.  Have them express this in terms of days or hours.  
One Million Pennies
One Billion Pennies


Monday, December 17, 2012

Purchasing Fictional Stocks For Math Class

The goal is for students to calculate values & percentage change of fictional stocks. One could easily have them graph results as well.

Getting students interested in investing and budgeting can start in your math class. Give each student $100 of play money and a copy of stock/commodity prices (easily found in Wall Street Journal or online). Have students scour the handout of stock prices and pick which stocks/commodities they would like to invest their $100 in. After doing so, have them calculate how many shares they purchased of each (round to the nearest tenth for ease).

Next, over the course of the next month, have them track their investment (either by you reproducing the pricing sheet or by them checking online). Each week have them recalculate their balance based on the change in stock price and the percentage change.


Change in Value:
$100 @ $25 per share = 4 shares.

If after 1 week the new price is $24 per share your investment is = $96 (4 x 24).

Percentage Change:

96 – 100 = - 4

- 4/100 = -.04 or – 4%

At the end of a designated time period, have students sell their shares and pay them back in pretend money.

**Differentiated Instruction: If you had some advanced students who really liked this exercise but wanted more, you could discuss short-term capital gains taxes and have students calculate their actual profit.  

Friday, December 14, 2012

Measuring Repulsion & Attraction With A Ruler

I love magnets! Even as a kid I enjoyed carrying magnets with me everywhere I went. I still remember the first time I stuck a magnet up to my grandmothers TV (Opps!). Although the study of magnetic properties can be pretty involving, magnets themselves offer great ways to bring simple lessons to life. In this lesson we will measure the effects of repulsion & attraction when two magnets interact. We will measure their interaction with a ruler.

What You Will Need

  • Rulers

  • Various Size/shape magnets (preferably labeled A, B, C...)

  • Activity Sheet


Students will use various magnets to measure repulsion and attraction. Using a ruler, students can use the same polarity to repel the other magnet and record the distance of that repulsion. Next, using the same two magnets, students can use opposite sides of polarity to measure the distance along the ruler from which two magnets attract one another (be careful with the fingers!)


Step 1: Create groups of partners and give each group a ruler, bag of magnets and activity sheet.

Step 2: Have groups spread out along the floor

Step 3: Have student pick two magnets and use a ruler to measure the distance upon which they attract, and repel.

Step 4: Filling in activity sheet

Activity Sheet

1) Magnet______ and Magnet_____

a) Attraction begins slightly at _______cm apart.

b) Repulsion begins slightly at _______cm apart

c) When set beside each other they repel ____cm distance

d) At ______cm the two magnet fully attract (snap together)

Wednesday, December 12, 2012

The Ultimate B-Day Expression

The purpose of this activity is to have some fun doing expression work. Students will substitute information into an expression with the end result being their birthday. Feel free to use calculators to make this a quick exercise. Here is the expression.

X = Month Of Your Birthday

Y = Day Of The Month Of Your Birthday

Note the vast amount of grouping symbols the kids will need to keep track of.

Example: My birthday is November 21st

x = 11
y = 21

My Math is thus

7(11) = 77
77 - 1 = 76
76(13) = 988
988+ 21 + 3 = 1012
1012(11) = 11132
11132 -11 -21 = 11100
11100/10 = 1110
1110 + 11 = 1121
1121/100 = 11.21 (11.21 is my b-day)

Monday, December 10, 2012

Firewood By The Truck-load: Volume & Per Unit Pricing

Let's assume you got behind on your firewood splitting and needed to purchase some firewood for a week till you get caught up. You check you local paper and see they have prices of $80 per truck-load. What can one expect from a truck-load of wood? How many units? How much is this per unit? We will be using some basic volume to get the number of units and use this number to get a per unit price. We could then decide how long it will last based on types of wood, etc (Note: The purpose of this activity is for the application more so than for the usefulness. As anyone whose ever split wood knows, quality has more to do with density and how well the wood is seasoned..see below)

Measurements Used
Full Size F-150 Long-bed Truck

Length = 8ft
Width = 6.5ft
Height = 1.6ft

Piece of Firewood (We will assume the average log length is 18inches and has a radius of 8 inches which will be cut into 8 pieces for firewood)

Units of Firewood by Volume

For the sake of ease, let us assume that a truckload of firewood will be neatly stacked but not higher than the sides of the truck.

Volume of truck bed

8x6.5x1.6 = 83.2ft^3

Volume of Firewood Log

Changing Our Units to feet

length = 18 inches = 1.5ft
radius = 8 inches = 0.66ft

Volume of a cylinder equals

V = (pi)(r^2)(h)
V = (3.14)(0.44)(1.5) = 2.05ft^3

Volume of Firewood Piece (once split into 8 pieces)

2.05ft^3 / 8 = 0.26ft^3

Units of Firewood Per Truckload

Now that we know the volume of both the truck-bed and for a piece of fire wood we can simply divide them to see how much firewood should stack neatly into the truck-bed

83.2 / 0.26 = 320 pieces of firewood

Adjusting For The Odd Shapes

Since the pieces of firewood are not cubic, they are circle-sections. They will not stack neatly together. There will be added spacing between them. The seller could compensate for this by stacking the firewood above the walls of their truck, but we will assume they didn't.

This spacing could be compensated with a little optimization. But, from stacking wood I think it would be safe to say that four every 10 pieces you will loose one to spacing. Thus we will loose 1/10th of our total to spacing. 1/10 of 320 = 32

320 – 32 = 288pieces of firewood.

Prices Per Unit

At the rate of $80 per truck-load. We have $80 per 288 pieces of wood

80/288 = $0.28 per unit.
The Calculations Are Quite Arbitrary

These calculations are quite arbitrary in their usefulness. Most firewood comes in different sizes. A true calculation of how good the deal on firewood would to compare volume to density as well as how seasoned. The purpose of this posting was simply to serve as an application.

From Here We Could

From here we could ask questions like.

1) If we use 40 pieces of firewood per night, how long will this last us?
2) If you wanted to, you could make a step-function based on how cold it is outside.

At 40 degrees we use 10 pieces of firewood per night
At 30 degrees we use 30 pieces of firewood per night

3) Could recalculate based on the volume questions for different size truck-beds or different materials

Friday, December 7, 2012

Addressing Our Probability Inefficiencies

The purpose of this activity is short but important. That is to help students NOT associate number of outcomes with probability of outcomes. One could probably teach this to their students faster than they can read this post.

The Problem:

Khan Academy (the wonderful, wonderful people they are) was asked by Lebron James what the chances of making 10 free throws in a row? I won't attempt to outdo Sal on this one

But I want to draw attention to what I find to be a more interesting problem. That is, why do students tend to associate the number of outcomes with the probability of outcomes? In other words, students tend to sometimes think of outcomes such as hit/miss, win/loose, yes/no, etc in terms of each result having a 50/50 chance. Or again, we tend to think that probabilities of outcomes are always distributed equally. This is a dangerous error to make in life, but the good news is that this is often more an academic mistake than a real-life mistake

For example, ask the following two questions to the same person and see what answers you get.

1) If you shoot a basketball, whats the chances of it going in?
2) If you shoot a full court shot, are you more likely to make it or miss it?

The Solution:

The good news is that you can quickly teach kids to be skeptical of this by taking them to a basketball hoop during activity time or gym class and asking the two questions above, then testing them.  

Wednesday, December 5, 2012

Variation Of "Bowling For Facts" Integers Addition

I love the creativity of elementary teachers! One notable project I found was First Grader At Last 

I will reproduce their idea below and then show you a variation of how it could be used for teaching higher level math.

Here is a recap of their project

From First Grader...At Last

Today during math stations, the kids went bowling for addition facts...without the real pins and bowling balls, but still pretty fun! This is a partner game, and each player gets a bowling mat and a handful of colorful chips (I call them mini bowling balls). The players take turns rolling 2 dice, then adding the sums of the numbers rolled. When one of the players rolls a number found on one of their pins, they "knock over" that pin with a chip. The first player to have all pins knocked over wins the game! “

Here is a variation of the game that would allow you to teach adding and subtracting integers.

Using red and white dice (red =negative numbers, white = positive numbers)

The new bowling mat would look something like

New Bowling Answer Sheet For Integers


Roll Both Dice
Red = 5
White = 2

-5 + 2 = -3

Monday, December 3, 2012

Polygonal Glasses & Superhero Masks

Need a fun way for students to learn different polygonal shapes? How about making some special polygonal glasses or masks? Notice the octogon shape lenses?

(Hey, no laughing at my horrible artwork!)

Today were going to expand our attire…polygonal style! The purpose of this activity is for groups of students to make their own masks or glasses while using different shaped lenses.

Here is a link to some printouts.