File:Battery-Heater-Resistor system.png

The batteries are in a series. Since the two 1.5 V batteries are in series with each other, that makes the batteries a total of 3 V together. The total power would be the total voltage squared (9 V^2) over resistance of 7.2 ohms, which equals 1.25 V. To find how long the battery would last, we had 16,000 mA over the number of resistor (3) times current (.42 A). The batteries should last 12.7 hours.