standard_description: Prove theorems about triangles. Theorems include: measures of interior angles of a triangle sum to 180°; base angles of isosceles triangles are congruent; the segment joining midpoints of two sides of a triangle is parallel to the third side and half the length; the medians of a triangle meet at a point.
problem_activity: Problem 1
Mr. Wynn now wants to cover a part of the gym with butcher paper to work on a large painting. He covers a section of the gym that is 30 feet long and 35 feet wide. Then he realizes he needs a bit more space for the painting and adds a section of butcher paper that is 4 feet long and 35 feet wide.
a.   How many square feet of butcher paper did Mr. Wynn use for his painting?
b.   What is the total length and width of Mr. Wynn’s painting?
Problem 2
a.   Label the area model to represent 31 × 23 and to find that product.
Decompose each number into its base-ten units (tens and ones) and write them in the boxes on each side of the rectangle.
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Label regions A, B, C, and D with their areas. Show your reasoning.
Find the product that the area model represents. Show your reasoning.
b.   Here is one way to calculate 31 × 23. Each number with a box gives the area of one region in the area model.
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In the boxes next to each number, write the letter of the corresponding region.
There is a 1 above the hundreds digit in the sum. What does that 1 represent?
Problem 3
Estimate each product. Then use any method to solve.
a.
$$26\times37$$
b.
$$81\times52$$
c.
$$68\times73$$


aligns: no