standard_description: Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.
problem_activity: Task
Suppose we are given a circle of radius $r$.  The goal of this task is to construct an equilateral triangle whose three vertices lie on the circle.
Suppose $\overline{AB}$ is a diameter of the circle.  Draw a circle with center $A$ and radius $r$ and label the two points of intersection of the circles $P$ and $Q$ as pictured below:
[IMG]
Show that $m(\angle ABP) = 30$ and $m(\angle ABQ) = 30$.
Show that
$\triangle PBQ$ is an equilateral triangle inscribed in the given circle.


aligns: no