This task is a refinement of ``Carbon 14 dating'' which focuses on accuracy. Because radioactive decay is an atomic process modeled by the laws of quantum mechanics, it is not possible to know with certainty when half of a given quantity of Carbon 14 atoms will decay. This type of question is very important in science and it also provides an opportunity to study the very subtle question of how errors behave when applying a function: in some cases the errors can be magnified while in others they are lessened.

This problem involves solving a system of algebraic equations from a context: depending how the problem is interpreted, there may be one equation or two.

This task is a somewhat more complicated version of "Accurately weighing pennies I'' as a third equation is needed in order to solve part (a) explicitly. Instead, students have to combine the algebraic techniques with some additional problem-solving (numerical reasoning, informed guess-and-check, etc.)

The solutions unit consists of the following: General points for discussion relating to the teaching of the mathematical content in the activities. Step-by-step mathematical solutions to the activities. Annotations to the solutions to assist teachers in their understanding the maths as well as teaching issues relating to the mathematical content represented in the activities. Suggestions of links to alternative activities for the teaching of the mathematical content represented in the activities.

The solutions unit consists of the following: General points for discussion relating to the teaching of the mathematical content in the activities. Step-by-step mathematical solutions to the activities. Annotations to the solutions to assist teachers in their understanding the maths as well as teaching issues relating to the mathematical content represented in the activities. Suggestions of links to alternative activities for the teaching of the mathematical content represented in the activities

The solutions unit consists of the following: General points for discussion relating to the teaching of the mathematical content in the activities. Step-by-step mathematical solutions to the activities. Annotations to the solutions to assist teachers in their understanding the maths as well as teaching issues relating to the mathematical content represented in the activities. Suggestions of links to alternative activities for the teaching of the mathematical content represented in the activities.

Spreadsheets Across the Curriculum module/Geology of National Parks course. Students estimate travel times and costs of a driving/camping trip to visit national parks in Colorado.

Using math templates during instruction keeps each student actively involved and allows the teacher to informally assess each student's proficiency with the skills and concepts addressed in the day's lesson. Many teachers regularly use whiteboards to have students record answers, write terms, draw pictures, etc. The use of templates in sheet protectors extends this practice and eliminates the time spent drawing diagrams, etc., allowing students more time to demonstrate mathematical proficiency. Teachers who regularly use math templates include planned task items that assess student proficiency. Careful observation of student responses allows teachers to form flexible small groups for additional instruction or enrichment and also better plan for instruction.

Effective measurement techniques include the concept of measurement uncertainty. Students may make erroneous conclusions analyzing data using measurements that do not include the uncertainty of the measurement. In this lab, students determine a density range for a metal and identify the material based on this range.

This is a lab activity that allows students to collect data to practice using effective measurement. While other authors have produced similar labs, this version includes uncertainty analysis consistent with effective measurement technique as presented in the module Measurement and Uncertainty.

An interactive applet and associated web page that demonstrate acute angles (those less than 90 deg). The applet presents an angle (initially acute) that the user can adjust by dragging the end points of the line segments forming the angle. As it changes it shows the angle measure and a message that indicate which type of angle it is. There a software 'detents' that make it easy capture exact angles such as 90 degrees and 180 degrees The message and angle measures can be turned off to facilitate classroom discussion. The text on the page has links to other pages defining each angle type in depth. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

An interactive applet and associated web page that demonstrate the three types of triangle: acute, obtuse and right. The applet shows a triangle that is initially acute (all angles less then 90 degrees) which the user can reshape by dragging any vertex. There is a message changes in real time while the triangle is being dragged that tells if the triangle is an acute, right or obtuse triangle and gives the reason why. By experimenting with the triangle student can develop an intuitive sense of the difference between these three classes of triangle. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.

This short video and interactive assessment activity is designed to teach fourth graders about multi-step addition of weights with compound units (metric units) - word problems.

This short video and interactive assessment activity is designed to teach fourth graders about adding compound units in years and months.

This short video and interactive assessment activity is designed to give fourth graders an overview of weight-based english-unit word problems.

This short video and interactive assessment activity is designed to teach fifth graders about converting integer and fraction sums into decimals.

This short video and interactive assessment activity is designed to give fifth graders an overview of measuring capacity (metric units).

This short video and interactive assessment activity is designed to give fourth graders an overview of measuring capacity (metric units).

This video and accompanying interactive assessment practice was designed to teach overview of addition sums to first graders.

This short video and interactive assessment activity is designed to teach second graders an overview of addition (sums to 100).