Keeping water supplies clean requires regular measurement of levels of pollutants. the measurements are indirect—a typical analysis involves forming a dye by a chemical reaction with the dissolved pollutant, then passing light through the solution and measuring its "absorbence." to calibrate such measurements, the laboratory measures known standard solutions and uses regression to relate absorbence and pollutant concentration. this is usually done every day. here is one series of data on the absorbence for different levels of nitrates. nitrates are measured in milligrams per liter of water.

nitrates 50 50 100 200 400 800 1200 1600 2000 2000
absorbence 7.0 7.6 12.7 24.0 47.0 93.0 138.0 183.0 231.0 226.0

the calibration process sets nitrate level and measures absorbence. the linear relationship that results is used to estimate the nitrate level in water from a measurement of absorbence.

a. what is the equation of the line used to estimate nitrate level?
b. what does the slope of this line say about the relationship between nitrate level and absorbence?
c. what is the estimated nitrate level in a water specimen with absorbence 40?

Antonio made a scale model of a building. the model's scale is 1 inch to 235 feet and its height is 3.5 inches. what is the exact height of the actual building? enter your answer in the box.

In δabc shown below, ∠bac is congruent to ∠bca: triangle abc, where angles a and c are congruent given: base ∠bac and ∠acb are congruent. prove: δabc is an isosceles triangle. when completed (fill in the blanks), the following paragraph proves that line segment ab is congruent to line segment bc making δabc an isosceles triangle. (4 points) construct a perpendicular bisector from point b to line segment ac . label the point of intersection between this perpendicular bisector and line segment ac as point d: m∠bda and m∠bdc is 90° by the definition of a perpendicular bisector. ∠bda is congruent to ∠bdc by the definition of congruent angles. line segment ad is congruent to line segment dc by by the definition of a perpendicular bisector. δbad is congruent to δbcd by the line segment ab is congruent to line segment bc because consequently, δabc is isosceles by definition of an isosceles triangle. 1. corresponding parts of congruent triangles are congruent (cpctc) 2. the definition of a perpendicular bisector 1. the definition of a perpendicular bisector 2. the definition of congruent angles 1. the definition of congruent angles 2. the definition of a perpendicular bisector 1. angle-side-angle (asa) postulate 2. corresponding parts of congruent triangles are congruent (cpctc)

Abaseball team drinks 10/4 gallons of water during a game. which mixed number represents the gallons of water consumed? a) 1 1/2 gallons b) 2 1/2 gallons c) 2 3/4 gallons d) 3 1/2 gallons