Activity 1.7 Darts
Teacher's Page
The object of the Darts game is to "pop" balloons located on a number line. The Darts are "thrown" by entering a number in fractional form.  Here is a glimpse of a game in progress. Two darts (3/4 & 5/8) have been thrown so far. Notice that 3/4 is too big and 5/8 is too small. 

What would be your next throw? Explain your strategy. 

Resources: Microworlds 2.03 or Pro (File: Dartsrb.mws*)

Environment: One computer classroom
Level: I

Strategy: Students working in cooperative groups

Standards (GEPA) Connections:

Description
Darts is a Microworlds activity that requires the player to pop a balloon that appears on a number line between 0 and 1 by throwing fractional darts.

Setting the Stage
Play this fraction game with the students. "I'm thinking of a fraction between 0 and 1.  Can you guess it? It must be stated in fractional form with a whole numbers for the numerator and denominator." (Choose 3/4 as your fraction to guess.)  A student may guess 1/2. You would say that his or her number is too small. Another student may say 7/8 to which you respond with that's too big. At this point the students may be stuck because they need to find a fraction that is between 1/2 and 7/8. Some students may realize that 3/4 is in between and would guess correctly. At this point show them the challenge problem and explain how Darts works. 

Doing the Activity
Hand out the student page and ask the students to explain mathematically how they found a number between 3/4 and 5/8.  Some possible anwers would include:

  • 7/10. I changed the numbers to decimals .75 and .625 and saw that .7 is in between. I would enter 7/10.
  • 4/6. 4 is between 3 and 6 is between 4 and 8. So I think 4/6 or 2/3 would work. (See diversion below)
  • 5.5/8 Make the two fractions have a common denominator so now we have 6/8 and 5/8. 
Debrief
Finding a number between 3/4 and 5/8 is challenging for students who have a fragile understanding of fractions. One strategy would be to look at 3/4 in an equivalent form, 6/8. Now the two numbers have a common denominator, but you need a number between 5/8 and 6/8. With fractional notation this is a difficult problem to "intuit" since we need to find a number between 5/8 & 6/8. Realizing that if we now write 5/8 as 10/16 and 6/8 as 12/16 then the number in between is 11/16. However, there is nothing wrong with an answer like  5.5 / 8. It's just that we are unaccostumed to mixing fractions and decimals. In fact, this problem is much easier if you convert to decimals. What's a number beween .75 and .625?. (Any number larger than .63 and smaller than .74 lives between 3/4 and 5/8)

Finish the lesson by playing Darts (Dartsrb.mws) on a one computer station. The class can be split into 2 teams and each team can take turns throwing an arrow. 

Extensions & Additional Activities
 Play a round of 5.
 

Balloon
Location
Throws?
1
   
2
   
3
   
4
   
5
   
 
TOTAL=
 

References

Websites

* Dartsrb.mws is available in Java format on the web at http://clime.org/microworlds. Permission for using the program is granted by Robert Berkman who holds the copyright. 

Diversion

A more interesting (though not necessarily pedagogically sound) way to find a number between 3/4 and 5/8 is to add the two numerators (3+5=8) and the two denominators (4+8=12) and form the fraction 8/12 (or 2/3) which happens to fall between the two original fractions. 2/3ís middle stature can be easily confirmed by looking at the three fractions with the common denominator 24. (18/24; 16/24; 15/24.). Was that just a coincidence or does that always work? It turns out that it always works. Hereís a proof. 
Copyright © 1999-2001 Stevens Institute of Technology Center for Improved Engineering and Science Education, All Rights Reserved.