standard_description: Subtract multiples of 10 in the range 10-90 from multiples of 10 in the range 10-90 (positive or zero differences), 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.
problem_activity: The square below has an area of
$${20}$$
square units.
[IMG]
Taylor writes the equation
$$s^2={20}$$
to find the measure of the side length of the square. She reasons that the solution to the equation is
$$\sqrt{20}$$
and concludes that the side length of the square is
$${10}$$
units.
Do you agree with Taylor? Explain why or why not. If you disagree, include the correct side length of the square.


aligns: no