PS/IS 686 | Brooklyn, NY

Fractions, Fractions, Everywhere!

Welcome Back!  I hope everyone had a wonderful week with your children.  We are continuing our fraction units in both 4th and 5th grades.  Here are some highlights that occurred before break.

In fourth grade, we wrapped up our sub sandwich investigation.  In our final exploration, we discussed that the only fair way to share all the sandwiches was to share the 17 sandwiches among the 22 students, giving each student 17/22 of a sandwich.  Since it would be really hard to cut each sandwich into 22 pieces, we explored landmarks. If we only wanted to make one cut, would 17/22 be closest to ½, 2/3 or ¾.  Below is some student work that displays their thinking.  It was great to see so many students using number lines and think about what halves, thirds, and fourths would be in relation to 22nds.


This week, we will be looking at equivalence a little more formally.  We will use pictures and number lines, and we will develop the idea of using multiplication to create equivalent fractions.  There will be a test either Friday or Monday.  

Fifth graders began their fraction unit with a problem that linked division to fractions.  They solved a problem where they compared the prices of cat food at 2 stores.  Maria’s store sold 2o cans of cat food for $23, while Bob’s store sold 12 cans for $15.  There was such a variety of strategies in the fifth grade!  Many students used division to find the unit rate.  This makes sense since we just finished our decimal unit.  Others, however, thought about using a ratio table or multiplication to find a common number of cans.  If we know the price for the same number of cans, we can see which is the better buy.  Still others used reasoning to think about how a difference of $3 distributed among more cans would mean less per can.  Take a look at some of their work.

This week, we will continue with investigations related to the pet stores.  Through these problems, we will be continuing to look at ratio, an important idea that will occur more formally in sixth grade.

Enjoy your week!