Use the unit multipliers to go from feet to miles, from miles to km and from km to meters. This can be done all at once using dimensional analysis.
[tex]\text{2640 feet}\dfrac{1 mile}{5280 feet}*\dfrac{1.6 km}{1 mile} * \dfrac{1000m}{1km}[/tex]
Next multiply all the numerators together. 2640 is part of the numerator expression
Numerators: 2640 * 1 * 1.6*1000 = 4224000
Denominators: 5280*1 * 1 = 5280
Now divide the numerators by the denominators
Numerator / denominator = 4224000 / 5280= 800
Answer: 2640 feet = 800 meters.