Concept explainers
HVAC We can estimate the cost CN (in dollars per million Btu) of a natural gas–powered heating system using the formula
where T is the cost per therm of natural gas and E is the operating efficiency of the system. Similarly, we can estimate the cost CA (also in dollars per million Btu) of an air-source heat pump using the formula
where K is the cost per kilowatt-hour of electricity and R is the efficiency rating of the pump. Assume the following:
- An existing natural-gas heater is 92% efficient. (Use 0.92.)
- A new air-source heat pump would have an efficiency rating of 9.5.
- Electricity costs $0.09 per kilowatt-hour.
What would the cost of natural gas have to be to make the two annual costs the same?
Want to see the full answer?
Check out a sample textbook solutionChapter 7 Solutions
Mathematics for the Trades: A Guided Approach (11th Edition) (What's New in Trade Math)
Additional Math Textbook Solutions
A Problem Solving Approach to Mathematics for Elementary School Teachers (12th Edition)
Fundamentals of Differential Equations and Boundary Value Problems
Thinking Mathematically (6th Edition)
Finite Mathematics (11th Edition)
- The Skydiver Again When a skydiver jumps from an airplane, her downward velocity, n feet per second, before she opens her parachute is given by = 176 1 0.834t, where t is the number of seconds that have elapsed since she jumped from the airplane. We found earlier that the terminal velocity for the skydiver is 176 feet per second. How long does it take for her to reach 90 of terminal velocity?arrow_forwardKinetic Energy The kinetic energy E of an object can be calculated by the formula E=12mv2, where m is the mass and v is the velocity. Solve for m.arrow_forwardForensics At 8:30 A.M., a coroner went to the home of a person who had died during the night. In order to estimate the time of death, the coroner took the person’s temperature twice. At 9:00 A.M. the temperature was 85.7F, and at 11:00 A.M. the temperature was 82.8F. From these two temperatures, the coroner was able to determine that the time elapsed since death and the body temperature were related by the formula t=10lnT7098.670 where t is the time in hours elapsed since the person died and T is the temperature (in degrees Fahrenheit) of the person’s body. (This formula comes from a general cooling principle called Newton’s Law of Cooling. It uses the assumptions that the person had a normal body temperature of 98.6F at death and that the room temperature was a constant 70F.) Use the formula to estimate the time of death of the person.arrow_forward
- Algebra & Trigonometry with Analytic GeometryAlgebraISBN:9781133382119Author:SwokowskiPublisher:CengageCollege AlgebraAlgebraISBN:9781305115545Author:James Stewart, Lothar Redlin, Saleem WatsonPublisher:Cengage LearningFunctions and Change: A Modeling Approach to Coll...AlgebraISBN:9781337111348Author:Bruce Crauder, Benny Evans, Alan NoellPublisher:Cengage Learning
- Algebra: Structure And Method, Book 1AlgebraISBN:9780395977224Author:Richard G. Brown, Mary P. Dolciani, Robert H. Sorgenfrey, William L. ColePublisher:McDougal LittellAlgebra and Trigonometry (MindTap Course List)AlgebraISBN:9781305071742Author:James Stewart, Lothar Redlin, Saleem WatsonPublisher:Cengage Learning