Sally said that when you add or subtract positive or negative decimals, you can change the order of the decimals and still get the same answer. Use these decimals to answer the questions: 6.2  , 5.71, 3.96  , 2.84 (a) Is Sally’s statement always true, sometimes true, or always false? Write two pairs of equations using addition and two pairs of equations using subtraction to support your answer. (b) Write a rule about changing the order of the numbers in adding and in subtracting positive and negative decimals. (c) Is Sally’s statement true for addition and subtraction of three positive or negative decimals? Write two pairs of equations (one pair for addition, and one pair for subtraction) that support your answer.

What are the solutions of the following system? y=-2x^2 y=x-2

Farmers know that driving heavy equipment on wet soil compresses the soil and injures future crops. here are data on the "penetrability" of the same type of soil at two levels of compression. penetrability is a measure of how much resistance plant roots will meet when they try to grow through the soil. compressed soil 2.85 2.66 3 2.82 2.76 2.81 2.78 3.08 2.94 2.86 3.08 2.82 2.78 2.98 3.00 2.78 2.96 2.90 3.18 3.16 intermediate soil 3.17 3.37 3.1 3.40 3.38 3.14 3.18 3.26 2.96 3.02 3.54 3.36 3.18 3.12 3.86 2.92 3.46 3.44 3.62 4.26 use the data, omitting the high outlier, to give a 95% confidence interval for the decrease in penetrability of compressed soil relative to intermediate soil. compute degrees of freedom using the conservative method. interval: to

Brittany has designed four different birdcages, each with the same volume: a square pyramid, a cylinder, a cone, and a sphere. the zoo wants to use one of brittany’s designs but plans to change the volume of the cage. find the design change that would result in the birdcage with the greatest volume. a.) increase the area of the base of the square pyramid by a factor of ten. b.) increase the height of the cylinder by a factor of ten. c.) increase the radius of the cone by a factor of ten. d.) increase the radius of a sphere by a factor of ten.