A 150-lb person burns about 2700 Calories to run a marathon. How much energy is burned in kJ?

The question above is simply asking us to convert the value from calories into kilojoules. Therefore, we need some factor to multiply to be able to convert it to such units. For calories to kJ, the factor would be 4.184.

2700 cal (4.184 kJ/cal) = 11296.8 kJ