Question

the temperature of substance decreases at the rate of 2 degree Celsius prr 10 minutes. the temperature of the substance at 5 o'clock was 10 degree Celsius. at what time will the temperature of the substance be 4 degree Celsius below zero?

Answer 1

The temperature of the substance at 5:30 is 4 degree celsius

Answer 2

The temperature of substance is 10 degree Celsius at 5 o' clock


The time needs to be calculated when the temperature of substance is -4 degree celsius (as it is mentioned that "4 degree Celsius below zero")

Therefore the drop in the temperature is 10 - (-4)
= 10 + 4
= 14 degrees

Let the total time required for this drop be x
For every 10 mins, there is a drop of 2 degree Celsius.

Therefore x/10 = 14/2
x = 14*10/2
x = 140/2
x = 70

So 70 minutes will be required for the substance to reach -4 degree Celsius.
70 minutes corresponds to 1 hour 10 minutes

Hence the time at which the substance would reach -4 degree Celsius is 5 o' clock +1hr 10 mins
= 6 hrs 10 mins