If the were 400 g sample of pond water and it has a concentration of 3.5 ppm dissolved nitrates.
what is the mass of dissolved nitrates in this sample?
note: converting atmospheric pollutant concentrations from ppmv to mg/m3 the conversion factor depends on the temperature at which you want the conversion (usually about 20 to 25 degrees centigrade). at an ambient pressure of 1 atmosphere, the general equation is: mg/m3 = (ppmv)(12.187)(mw) / (273.15 + °c) where: mg/m3= milligrams of gaseous pollutant per cubic meter of ambient air, ppmv= ppm by volume (i. e., volume of gaseous pollutant per 106 volumes of ambient air), mw= molecular weight of the gaseous pollutant, and °c= ambient air temperature in degrees centigrade

Mrs. julien’s and mrs. castillejo’s classes are selling cookie dough for a school fundraiser. customers can buy packages of macadamia nut chip cookie dough and packages of triple chocolate cookie dough. mrs. julien’s class sold 25 packages of macadamia nut chip cookie dough and 30 packages of triple chocolate cookie dough for a total of $221.25. mrs. castillejo’s class sold 5 packages of macadamia nut chip cookie dough and 45 packages of triple chocolate cookie dough for a total of $191.25. (a) write the system of equations that model the problem. be sure to explain which equation represents which situation. (b) find the cost of each type of cookie. show your work. (c) explain which method you used to solve the system and why you chose that method.