If the price of electrical energy is $0.10 per kilowatt · hour, what is the cost of using electrical energy to heat the water in a swimming pool (11.0 m ✕ 9.00 m ✕ 2.5 m) from 17 to 22° C?
does the teacher even know the answer?
since the density of water is 1000kg/m^3
and the specific heat of water is 4190 kJ/kg-°C we have
247.5 m^3 * 1000kg/m^3 * 4190kJ/kg-°C * 5°C = 5.185*10^9 kJ
now, since 1 kw-hr = 3600 kJ the cost is
5.185*10^9kJ * 1kwh/3600kJ * $0.1/kwh = $144,031.25
Hmmm. That seems awfully high. Better check my math ...