This is an entire unit of activities relating to whole numbers, place value and rounding.  The activity I use is called "Reality Checking" on pages 57-64.  "Reality Checking" provides a real world connection for students to practice and apply the standard algorithm for addition and subtraction.  Students will work either individually, with a partner or group to balance a mock checking account.  Students will add whole number deposits and subtract whole number withdrawals while using estimation to check for reasonableness.

Students will be given a sheet with shape names on it.  They will draw several two-dimensional shapes using the information that they already know about.  They will look over their shapes and compare them, first to their other shapes and then to other students.  While doing this the students will look at what attributes make up the different shapes.  They will also compare and contrast their own shapes.

Students will respresent and compare decimals at they collect data.  For part 1 students work with a partner to each take 10 shots at the trash can with wads of paper.  Before shooting students predict how many they will make.  While shooting students record their results with tallies.  Then they write the results as a fraction and as a decimal.  Students create a poster and compare their data.  Then they write to explain the results and prepare to share their results with the class. Part 2 requires students to combine their data with the data of 9 other classmates.  After recording the data, students create a poster with the data and write to explain the results.  Students then share their results with the class.