Education Development Center
Micro-Geography of the Number Line
Young mathematicians dive into the number line to discover decimals and how the numbers infinitely get smaller in between. They click the zoom button a few times and learn that the number line doesn't just stop at integers. Includes a...
Curated OER
Rounding and Subtracting
Common Core is all about getting your learners to open their minds and think about the why and how. This problem has them thinking about unknown numbers and their relationship with one another when we round and subtract. They will have...
Illustrative Mathematics
Two Wheels and a Belt
Geometry gets an engineering treatment in an exercise involving a belt wrapped around two wheels of different dimensions. Along with the wheels, this belt problem connects concepts of right triangles, tangent lines, arc length, and...
EngageNY
Estimating Centers and Interpreting the Mean as a Balance Point
How do you balance a set of data? Using a ruler and some coins, learners determine whether the balance point is always in the middle. Through class and small group discussions, they find that the mean is the the best estimate of the...
EngageNY
Understanding Variability When Estimating a Population Proportion
Estimate the proportion in a population using sampling. The 20th installment in a series of 25 introduces how to determine proportions of categorical data within a population. Groups take random samples from a bag of cubes to determine...
Illustrative Mathematics
The Lighthouse Problem
Long considered the symbol of safe harbor and steadfast waiting, the lighthouse gets a mathematical treatment. The straightforward question of distance to the horizon is carefully presented, followed by a look into the different...