From \(1970\) to \(1990\) the average per person annual consumption of whole milk declined at a constant rate from \(101\) to \(41\) quarts per year. During the same period, the average annual consumption of low fat milk increased at a constant rate from \(25\) to \(60\) quarts per year. What was the average annual per person consumption when the consumption of whole milk and low fat milk was the same?Choose 1 answer:(A) \(53\) quarts(B) \(55\) quarts(C) \(57\) quarts(D) \(59\) quarts
Q. From \(1970\) to \(1990\) the average per person annual consumption of whole milk declined at a constant rate from \(101\) to \(41\) quarts per year. During the same period, the average annual consumption of low fat milk increased at a constant rate from \(25\) to \(60\) quarts per year. What was the average annual per person consumption when the consumption of whole milk and low fat milk was the same?Choose 1 answer:(A) \(53\) quarts(B) \(55\) quarts(C) \(57\) quarts(D) \(59\) quarts
Determine rate of decline for whole milk: Determine the rate of decline for whole milk consumption.The decline in whole milk consumption over 20 years (from 1970 to 1990) is from 101 quarts to 41 quarts. This is a total decline of 101−41=60 quarts over 20 years.Rate of decline for whole milk=Number of yearsTotal decline=20 years60 quarts=3 quarts per year
Determine rate of increase for low fat milk: Determine the rate of increase for low fat milk consumption.The increase in low fat milk consumption over the same 20 years is from 25 quarts to 60 quarts. This is a total increase of 60−25=35 quarts over 20 years.Rate of increase for low fat milk=Number of yearsTotal increase=20 years35 quarts=1.75quarts per year
Set up equation for equal milk consumption: Set up an equation to find the year when the consumption of whole milk and low fat milk was the same.Let x be the number of years after 1970 when the consumptions are equal.Starting with 101 quarts for whole milk and subtracting 3 quarts per year, we get: 101−3x.Starting with 25 quarts for low fat milk and adding 1.75 quarts per year, we get: 25+1.75x.Set the two expressions equal to each other: 101−3x=25+1.75x
Solve equation for x: Solve the equation for x.Combine like terms: 101−25=3x+1.75x76=4.75xDivide both sides by 4.75 to solve for x: x=4.7576x≈16
Calculate average annual consumption: Calculate the average annual per person consumption when the consumptions are equal.Substitute x back into either the whole milk or low fat milk equation: 101−3(16) or 25+1.75(16).Using the whole milk equation: 101−3(16)=101−48=53 quarts.Using the low fat milk equation: 25+1.75(16)=25+28=53 quarts.Both equations should give the same result, which is the point where the consumptions are equal.
More problems from Interpret parts of quadratic expressions: word problems