Answer:
The water level drop in temperature per hour is 40 °C per hour
Unit rate
Hours between 10 P.M. and 7:36 A.M = 9 hours 36 minutes
= 9.6 hours
The total decrease in temperature = 6/25
The unit rate of decrease in temperature per hour = Hours between 10 P.M. and 7:36 A.M ÷ Total drop in temperature
= 9.6 ÷ 6/25
= 9.6 × 25/6
= 240/6
= 40 °C per hour
Therefore, the water level drop in temperature per hour is 40 °C.