By the definition, pressure is the force over the area on which it is exerted, `P = F/A.` If we cannot be sure that this ratio is the same for all parts of the area, then the force divided by the area is the average pressure. Also the force in the definition is supposed to be perpendicular to the area, which is true for horizontal floor and the gravity force.
The unit for pressure is Pascal, abbreviated Pa. It is equal to one Newton over one square meter.
In this problem both the force and the pressure are given, it is simple to find the area: `A = F/P = 250/5000 = 0.05 (m^2).` I hope the boy has two soles, so the area of one of them is twice less, `0.025 m^2,` or `250 cm^2.`
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