what day did he make the switch?

Question

On January 1, Dakota decides to drink one bottle of costlee calorik cola every day if the year. One 20 ounce bottle costs $1.29. Partway through the year, he starts buying 12 ounce bottles for $0.89 each to save money.at the end of the year he had spent the spend the same amount of money on 12 ounce as on 20 ounce bottles. What day did he make the switch? (assume their 365 day in a year)

Answer 1

Let's call D the day of the switch, so the cost up to the switch is 1.29D and the cost after the switch is 0.89(365-D).

1.29D=0.89(365-D); 1.29D=324.85-0.89D; 2.18D=324.85, so D=149. This corresponds to May 29.