sequences and series word problem

Question

a can of coke is taken out of the refrigerator at a temperature of 36 degrees Fahrenheit. in the first 10 minutes out of the refrigerator its temperature rises 10 degrees. in each 10 minute interval after that, the temperature rises 73% as much as it rose in the previous interval.

a.how much does the temperature rise during the 4th interval

b. how much has the temperature risen after 50 minutes (after 5 minute intervals)

c. what will the temperature of the coke be if it is left out forever

Answer 1

a_n = 10(0.73)^n-1

a₄ = 10(0.73)³

S₅ = 10(1 - 0.73⁵) / (1 - 0.73)

S = 36 + [(10) / (1 - 0.73)]