This problem introduces a logistic growth model in the concrete setting of estimating the population of the U.S. The model gives a surprisingly accurate estimate and this should be contrasted with linear and exponential models, studied in ``U.S. Population 1790-1860.'' This task requires students to interpret data presented.

In this activity students compare objects to see which is longer and heavier than the other.

In this task students figure out how to draw the longest line on a map of the United States without hitting a border. They use color and line plots to keep track of their results.

This task builds on studentsŐ prior knowledge and understanding of conditional probability, and introduces the concept of independence of events.

The purpose of this task is for students to compare two options for a prize where the value of one is given $2 at a time, giving them an opportunity to "work with equal groups of objects to gain foundations for multiplication." This context also provides students with an introduction to the concept of delayed gratification, or resisting an immediate reward and waiting for a later reward, while working with money.

The purpose of this task is for students to find different pairs of numbers that sum to 9.

This instructional task gives students a hands-on experience with composing and decomposing geometric figures.

This task is for students who know how to use base 10 blocks.

This task is a straightforward task related to adding fractions with the same denominator. The main purpose is to emphasize that there are many ways to decompose a fraction as a sum of fractions, similar to decompositions of whole numbers that students should have seen in earlier grades.

This tasks lends itself very well to multiple solution methods. Students may learn a lot by comparing different methods. Students who are already comfortable with fraction multiplication can go straight to the numeric solutions given below. Students who are still unsure of the meanings of these operations can draw pictures or diagrams.

This is the first of two fraction division tasks that use similar contexts to highlight the difference between the ŇNumber of Groups UnknownÓ a.k.a. ŇHow many groups?Ó (Variation 1) and ŇGroup Size UnknownÓ a.k.a. ŇHow many in each group?Ó (Variation 2) division problems.

This is the second of two fraction division tasks that use similar contexts to highlight the difference between the ŇNumber of Groups UnknownÓ a.k.a. ŇHow many groups?Ó (Variation 1) and ŇGroup Size UnknownÓ a.k.a. ŇHow many in each group?Ó (Variation 2) division problems.

The purpose of this instructional task is to motivate a discussion about adding fractions and the meaning of the common denominator. The different parts of the task have students moving back and forth between the abstract representation of the fractions and the meaning of the fractions in the context.

This task requires students to study the make-a-ten strategy that they should already know and use intuitively. In this strategy, knowledge of which sums make a ten, together with some of the properties of addition and subtraction, are used to evaluate sums which are larger than 10.

This task is to introduce students to the concept of reading an analog clock.

Making a 10 provides a technique to help students master single digit addition. The task is designed to help students visualize where the 10's are on a single digit addition table and explain why this is so. This knowledge can then be used to help them learn the addition table.

The purpose of this task is to generate a classroom discussion about ratios and unit rates in context.

This task is designed as an instructional task to develop students understanding of how data from a random sample can be used to estimate a population proportion or percentage.

The purpose of this task is to illustrate the development of margin of error when estimating a population mean.

This task provides three types of comparison problems: Those with an unknown difference and two known numbers; those with a known difference and a bigger unknown number; and those with a known difference and smaller unknown number. Students may solve each type using addition or subtraction, although the language in specific problems tends to favor one approach over another.