Answer: D(t)= 50(4/5)^t
Explanation: If 1/5 of the temperature difference is lost each minute, that means 4/5 of the difference remains each minute. So each minute, the temperature difference is multiplied by a factor of 4/5 (or 0.8).
If we start with the initial temperature difference, 50° Celsius, and keep multiplying by 4/5, this function gives us the temperature difference t minutes after the cake was put in the cooler.
Answer: 
The following vectors have been given: 
The angle between these two vectors can be found by:




Compare the initial mass to the final mass.
The answer is true I think
Let the height where we are trapped is H
now to find the time to reach the key at the bottom is given as

now we have


now if the speed of sound is considered to be 340 m/s then time taken by the sound to reach at the top is given as

now the total time is given as

now by solving above equation we have
H = 48 m
now height of one floor is 3 m
so our position must be
