Curtis measured the temperature of water in a flask in Science class. The temperature of the water was 35°C. He carefully heated the flask so that the temperature of the water increased about 2°C every 3 minutes. Approximately how much had the temperature of the water increased after 20 minutes?
The water temperature increased by about 2° every 3 minutes, or of a degree every minute. Multiplying the increase in degrees per minute by the total number of minutes yields
Since the problem asks for the increase in temperature and not the total temperature that results after the increases, 13 is the closest to our answer.