the temp ature of a liquad starts at 72°f and drops 2° per second the liquid is not supposed to drop below 40° f let s represent the number of seconds.
How many seconds does it take to get to 40° f?
Drop per second is 2°
Let total temp drop over time be Dt = 2s°, where s is the number of seconds.
Then current temperature is starting temperature minus total temp drop. i.e.
T = Ts – Dt, or
T = 72° - 2s°,
When the temperature is 40° f, i.e. T = 40° f, then
40 = 72 – 2s
2s = 72 – 40
2s = 32
s = 16
Answer: it will take 16 secs to get to 40° f