Answer:
2.7 Pizzas.
Explanation:
The power required to walk through 5km in 1 hour is 380W.
A watt is basically Jules per second, then we need to standardized this measurement to second.
5km/hr is equal to,
[tex]\frac{5km}{hr}*\frac{1hr}{3600s}*\frac{1000m}{1km}=1.389m/s[/tex]
Walking by 2.5 hours is equal to a distance of,
[tex]d=v*t=1.389*(2.5*3600) = 12500m[/tex]
The total energy required then would be,
[tex]E = \frac{380J}{1.389m/s}(12500)=3.4199*10^6J[/tex]
Then we know that one pizza slice gives [tex]1260*10^3J[/tex] of energy, the total pizza needed are,
[tex]\eta = \frac{3.4199*10^6}{1260*10^3} = 2.7142[/tex]
Then you need to buy 3 pizza.